From 0fc4dcc13f090c941abfab453a24945a4005b350 Mon Sep 17 00:00:00 2001 From: Toke Høiland-Jørgensen Date: Tue, 29 Jun 2021 11:39:07 +0200 Subject: bpf, devmap: Convert remaining READ_ONCE() to rcu_dereference_check() MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There were a couple of READ_ONCE()-invocations left-over by the devmap RCU conversion. Convert these to rcu_dereference_check() as well to avoid complaints from sparse. Fixes: 782347b6bcad ("xdp: Add proper __rcu annotations to redirect map entries") Reported-by: kernel test robot Signed-off-by: Toke Høiland-Jørgensen Signed-off-by: Daniel Borkmann Reviewed-by: Paul E. McKenney Acked-by: Martin KaFai Lau Link: https://lore.kernel.org/bpf/20210629093907.573598-1-toke@redhat.com --- kernel/bpf/devmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c index 2546dafd6672..fdc20892837c 100644 --- a/kernel/bpf/devmap.c +++ b/kernel/bpf/devmap.c @@ -558,7 +558,8 @@ int dev_map_enqueue_multi(struct xdp_buff *xdp, struct net_device *dev_rx, if (map->map_type == BPF_MAP_TYPE_DEVMAP) { for (i = 0; i < map->max_entries; i++) { - dst = READ_ONCE(dtab->netdev_map[i]); + dst = rcu_dereference_check(dtab->netdev_map[i], + rcu_read_lock_bh_held()); if (!is_valid_dst(dst, xdp, exclude_ifindex)) continue; @@ -654,7 +655,8 @@ int dev_map_redirect_multi(struct net_device *dev, struct sk_buff *skb, if (map->map_type == BPF_MAP_TYPE_DEVMAP) { for (i = 0; i < map->max_entries; i++) { - dst = READ_ONCE(dtab->netdev_map[i]); + dst = rcu_dereference_check(dtab->netdev_map[i], + rcu_read_lock_bh_held()); if (!dst || dst->dev->ifindex == exclude_ifindex) continue; -- cgit v1.3-14-g43fede From 22b6d14992b733e9421a475f4d43df24629737ab Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 4 Jun 2021 12:37:44 -0700 Subject: scftorture: Avoid false-positive warnings in scftorture_invoker() If the call to set_cpus_allowed_ptr() in scftorture_invoker() fails, a later WARN_ONCE() complains. But with the advent of 570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed"), this complaint can be drowned out by complaints from smp_processor_id(). The rationale for this change is that scftorture's kthreads are not marked with PF_NO_SETAFFINITY, which means that a system administrator could change affinity at any time. However, scftorture is a torture test, and the system administrator might well have a valid test-the-test reason for changing affinity. This commit therefore changes to raw_smp_processor_id() in order to avoid the noise, and also adds a WARN_ON_ONCE() to the call to set_cpus_allowed_ptr() in order to directly detect immediate failure. There is no WARN_ON_ONCE() within the test loop, allowing human-reflex-based affinity resetting, if desired. Signed-off-by: Paul E. McKenney --- kernel/scftorture.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/scftorture.c b/kernel/scftorture.c index 2377cbb32474..29e8fc5d91a7 100644 --- a/kernel/scftorture.c +++ b/kernel/scftorture.c @@ -405,15 +405,15 @@ static int scftorture_invoker(void *arg) VERBOSE_SCFTORTOUT("scftorture_invoker %d: task started", scfp->cpu); cpu = scfp->cpu % nr_cpu_ids; - set_cpus_allowed_ptr(current, cpumask_of(cpu)); + WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(cpu))); set_user_nice(current, MAX_NICE); if (holdoff) schedule_timeout_interruptible(holdoff * HZ); - VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, smp_processor_id()); + VERBOSE_SCFTORTOUT("scftorture_invoker %d: Waiting for all SCF torturers from cpu %d", scfp->cpu, raw_smp_processor_id()); // Make sure that the CPU is affinitized appropriately during testing. - curcpu = smp_processor_id(); + curcpu = raw_smp_processor_id(); WARN_ONCE(curcpu != scfp->cpu % nr_cpu_ids, "%s: Wanted CPU %d, running on %d, nr_cpu_ids = %d\n", __func__, scfp->cpu, curcpu, nr_cpu_ids); -- cgit v1.3-14-g43fede From 05bc276cf243d90b9f1eb6ae2962f41eeb53a741 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 10 Jun 2021 09:24:43 -0700 Subject: refscale: Avoid false-positive warnings in ref_scale_reader() If the call to set_cpus_allowed_ptr() in ref_scale_reader() fails, a later WARN_ONCE() complains. But with the advent of 570a752b7a9b ("lib/smp_processor_id: Use is_percpu_thread() instead of nr_cpus_allowed"), this complaint can be drowned out by complaints from smp_processor_id(). The rationale for this change is that refscale's kthreads are not marked with PF_NO_SETAFFINITY, which means that a system administrator could change affinity at any time. However, refscale is a performance/stress test, and the system administrator might well have a valid test-the-test reason for changing affinity. This commit therefore changes to raw_smp_processor_id() in order to avoid the noise, and also adds a WARN_ON_ONCE() to the call to set_cpus_allowed_ptr() in order to directly detect immediate failure. There is no WARN_ON_ONCE() within the test loop, allowing human-reflex-based affinity resetting, if desired. Signed-off-by: Paul E. McKenney --- kernel/rcu/refscale.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 313d4547cbc7..d998a76fb542 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -487,13 +487,13 @@ ref_scale_reader(void *arg) s64 duration; VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: task started", me); - set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)); + WARN_ON_ONCE(set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids))); set_user_nice(current, MAX_NICE); atomic_inc(&n_init); if (holdoff) schedule_timeout_interruptible(holdoff * HZ); repeat: - VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, smp_processor_id()); + VERBOSE_SCALEOUT_BATCH("ref_scale_reader %ld: waiting to start next experiment on cpu %d", me, raw_smp_processor_id()); // Wait for signal that this reader can start. wait_event(rt->wq, (atomic_read(&nreaders_exp) && smp_load_acquire(&rt->start_reader)) || @@ -503,7 +503,7 @@ repeat: goto end; // Make sure that the CPU is affinitized appropriately during testing. - WARN_ON_ONCE(smp_processor_id() != me); + WARN_ON_ONCE(raw_smp_processor_id() != me); WRITE_ONCE(rt->start_reader, 0); if (!atomic_dec_return(&n_started)) -- cgit v1.3-14-g43fede From 1d10bf55d85d34eb73dd8263635f43fd72135d2d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 25 May 2021 10:12:45 -0700 Subject: rcu-tasks: Don't delete holdouts within trc_inspect_reader() As Yanfei pointed out, although invoking trc_del_holdout() is safe from the viewpoint of the integrity of the holdout list itself, the put_task_struct() invoked by trc_del_holdout() can result in use-after-free errors due to later accesses to this task_struct structure by the RCU Tasks Trace grace-period kthread. This commit therefore removes this call to trc_del_holdout() from trc_inspect_reader() in favor of the grace-period thread's existing call to trc_del_holdout(), thus eliminating that particular class of use-after-free errors. Reported-by: "Xu, Yanfei" Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 03a118d1c003..3d5cb6cb8a6d 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -953,10 +953,9 @@ static bool trc_inspect_reader(struct task_struct *t, void *arg) in_qs = likely(!t->trc_reader_nesting); } - // Mark as checked. Because this is called from the grace-period - // kthread, also remove the task from the holdout list. + // Mark as checked so that the grace-period kthread will + // remove it from the holdout list. t->trc_reader_checked = true; - trc_del_holdout(t); if (in_qs) return true; // Already in quiescent state, done!!! -- cgit v1.3-14-g43fede From a9ab9cce9367a2cc02a3c7eb57a004dc0b8f380d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 25 May 2021 11:28:40 -0700 Subject: rcu-tasks: Don't delete holdouts within trc_wait_for_one_reader() Invoking trc_del_holdout() from within trc_wait_for_one_reader() is only a performance optimization because the RCU Tasks Trace grace-period kthread will eventually do this within check_all_holdout_tasks_trace(). But it is not a particularly important performance optimization because it only applies to the grace-period kthread, of which there is but one. This commit therefore removes this invocation of trc_del_holdout() in favor of the one in check_all_holdout_tasks_trace() in the grace-period kthread. Reported-by: "Xu, Yanfei" Signed-off-by: Paul E. McKenney --- kernel/rcu/tasks.h | 1 - 1 file changed, 1 deletion(-) (limited to 'kernel') diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 3d5cb6cb8a6d..8536c55df514 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -982,7 +982,6 @@ static void trc_wait_for_one_reader(struct task_struct *t, // The current task had better be in a quiescent state. if (t == current) { t->trc_reader_checked = true; - trc_del_holdout(t); WARN_ON_ONCE(t->trc_reader_nesting); return; } -- cgit v1.3-14-g43fede From 2a2ed5618a0e8a890d948b88b368c0459f35136c Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Sun, 4 Jul 2021 13:59:35 -0700 Subject: rcu: Fix pr_info() formats and values in show_rcu_gp_kthreads() This commit changes from "%lx" to "%x" and from "0x1ffffL" to "0x1ffff" to match the change in type between the old field ->state (unsigned long) and the new field ->__state (unsigned int). Signed-off-by: Paul E. McKenney --- kernel/rcu/tree_stall.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 3f937b20814f..6c76988cc019 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -795,9 +795,9 @@ void show_rcu_gp_kthreads(void) jr = j - data_race(rcu_state.gp_req_activity); js = j - data_race(rcu_state.gp_start); jw = j - data_race(rcu_state.gp_wake_time); - pr_info("%s: wait state: %s(%d) ->state: %#lx ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n", + pr_info("%s: wait state: %s(%d) ->state: %#x ->rt_priority %u delta ->gp_start %lu ->gp_activity %lu ->gp_req_activity %lu ->gp_wake_time %lu ->gp_wake_seq %ld ->gp_seq %ld ->gp_seq_needed %ld ->gp_max %lu ->gp_flags %#x\n", rcu_state.name, gp_state_getname(rcu_state.gp_state), - rcu_state.gp_state, t ? t->__state : 0x1ffffL, t ? t->rt_priority : 0xffU, + rcu_state.gp_state, t ? t->__state : 0x1ffff, t ? t->rt_priority : 0xffU, js, ja, jr, jw, (long)data_race(rcu_state.gp_wake_seq), (long)data_race(rcu_state.gp_seq), (long)data_race(rcu_get_root()->gp_seq_needed), -- cgit v1.3-14-g43fede From f263a81451c12da5a342d90572e317e611846f2c Mon Sep 17 00:00:00 2001 From: John Fastabend Date: Wed, 7 Jul 2021 15:38:47 -0700 Subject: bpf: Track subprog poke descriptors correctly and fix use-after-free Subprograms are calling map_poke_track(), but on program release there is no hook to call map_poke_untrack(). However, on program release, the aux memory (and poke descriptor table) is freed even though we still have a reference to it in the element list of the map aux data. When we run map_poke_run(), we then end up accessing free'd memory, triggering KASAN in prog_array_map_poke_run(): [...] [ 402.824689] BUG: KASAN: use-after-free in prog_array_map_poke_run+0xc2/0x34e [ 402.824698] Read of size 4 at addr ffff8881905a7940 by task hubble-fgs/4337 [ 402.824705] CPU: 1 PID: 4337 Comm: hubble-fgs Tainted: G I 5.12.0+ #399 [ 402.824715] Call Trace: [ 402.824719] dump_stack+0x93/0xc2 [ 402.824727] print_address_description.constprop.0+0x1a/0x140 [ 402.824736] ? prog_array_map_poke_run+0xc2/0x34e [ 402.824740] ? prog_array_map_poke_run+0xc2/0x34e [ 402.824744] kasan_report.cold+0x7c/0xd8 [ 402.824752] ? prog_array_map_poke_run+0xc2/0x34e [ 402.824757] prog_array_map_poke_run+0xc2/0x34e [ 402.824765] bpf_fd_array_map_update_elem+0x124/0x1a0 [...] The elements concerned are walked as follows: for (i = 0; i < elem->aux->size_poke_tab; i++) { poke = &elem->aux->poke_tab[i]; [...] The access to size_poke_tab is a 4 byte read, verified by checking offsets in the KASAN dump: [ 402.825004] The buggy address belongs to the object at ffff8881905a7800 which belongs to the cache kmalloc-1k of size 1024 [ 402.825008] The buggy address is located 320 bytes inside of 1024-byte region [ffff8881905a7800, ffff8881905a7c00) The pahole output of bpf_prog_aux: struct bpf_prog_aux { [...] /* --- cacheline 5 boundary (320 bytes) --- */ u32 size_poke_tab; /* 320 4 */ [...] In general, subprograms do not necessarily manage their own data structures. For example, BTF func_info and linfo are just pointers to the main program structure. This allows reference counting and cleanup to be done on the latter which simplifies their management a bit. The aux->poke_tab struct, however, did not follow this logic. The initial proposed fix for this use-after-free bug further embedded poke data tracking into the subprogram with proper reference counting. However, Daniel and Alexei questioned why we were treating these objects special; I agree, its unnecessary. The fix here removes the per subprogram poke table allocation and map tracking and instead simply points the aux->poke_tab pointer at the main programs poke table. This way, map tracking is simplified to the main program and we do not need to manage them per subprogram. This also means, bpf_prog_free_deferred(), which unwinds the program reference counting and kfrees objects, needs to ensure that we don't try to double free the poke_tab when free'ing the subprog structures. This is easily solved by NULL'ing the poke_tab pointer. The second detail is to ensure that per subprogram JIT logic only does fixups on poke_tab[] entries it owns. To do this, we add a pointer in the poke structure to point at the subprogram value so JITs can easily check while walking the poke_tab structure if the current entry belongs to the current program. The aux pointer is stable and therefore suitable for such comparison. On the jit_subprogs() error path, we omit cleaning up the poke->aux field because these are only ever referenced from the JIT side, but on error we will never make it to the JIT, so its fine to leave them dangling. Removing these pointers would complicate the error path for no reason. However, we do need to untrack all poke descriptors from the main program as otherwise they could race with the freeing of JIT memory from the subprograms. Lastly, a748c6975dea3 ("bpf: propagate poke descriptors to subprograms") had an off-by-one on the subprogram instruction index range check as it was testing 'insn_idx >= subprog_start && insn_idx <= subprog_end'. However, subprog_end is the next subprogram's start instruction. Fixes: a748c6975dea3 ("bpf: propagate poke descriptors to subprograms") Signed-off-by: John Fastabend Signed-off-by: Alexei Starovoitov Co-developed-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Link: https://lore.kernel.org/bpf/20210707223848.14580-2-john.fastabend@gmail.com --- arch/x86/net/bpf_jit_comp.c | 3 +++ include/linux/bpf.h | 1 + kernel/bpf/core.c | 8 +++++- kernel/bpf/verifier.c | 60 ++++++++++++++++----------------------------- 4 files changed, 32 insertions(+), 40 deletions(-) (limited to 'kernel') diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index e835164189f1..4b951458c9fc 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -570,6 +570,9 @@ static void bpf_tail_call_direct_fixup(struct bpf_prog *prog) for (i = 0; i < prog->aux->size_poke_tab; i++) { poke = &prog->aux->poke_tab[i]; + if (poke->aux && poke->aux != prog->aux) + continue; + WARN_ON_ONCE(READ_ONCE(poke->tailcall_target_stable)); if (poke->reason != BPF_POKE_REASON_TAIL_CALL) diff --git a/include/linux/bpf.h b/include/linux/bpf.h index f309fc1509f2..e8e2b0393ca9 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -780,6 +780,7 @@ struct bpf_jit_poke_descriptor { void *tailcall_target; void *tailcall_bypass; void *bypass_addr; + void *aux; union { struct { struct bpf_map *map; diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 034ad93a1ad7..9b1577498373 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2236,8 +2236,14 @@ static void bpf_prog_free_deferred(struct work_struct *work) #endif if (aux->dst_trampoline) bpf_trampoline_put(aux->dst_trampoline); - for (i = 0; i < aux->func_cnt; i++) + for (i = 0; i < aux->func_cnt; i++) { + /* We can just unlink the subprog poke descriptor table as + * it was originally linked to the main program and is also + * released along with it. + */ + aux->func[i]->aux->poke_tab = NULL; bpf_jit_free(aux->func[i]); + } if (aux->func_cnt) { kfree(aux->func); bpf_prog_unlock_free(aux->prog); diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index be38bb930bf1..42a4063de7cd 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12121,33 +12121,19 @@ static int jit_subprogs(struct bpf_verifier_env *env) goto out_free; func[i]->is_func = 1; func[i]->aux->func_idx = i; - /* the btf and func_info will be freed only at prog->aux */ + /* Below members will be freed only at prog->aux */ func[i]->aux->btf = prog->aux->btf; func[i]->aux->func_info = prog->aux->func_info; + func[i]->aux->poke_tab = prog->aux->poke_tab; + func[i]->aux->size_poke_tab = prog->aux->size_poke_tab; for (j = 0; j < prog->aux->size_poke_tab; j++) { - u32 insn_idx = prog->aux->poke_tab[j].insn_idx; - int ret; + struct bpf_jit_poke_descriptor *poke; - if (!(insn_idx >= subprog_start && - insn_idx <= subprog_end)) - continue; - - ret = bpf_jit_add_poke_descriptor(func[i], - &prog->aux->poke_tab[j]); - if (ret < 0) { - verbose(env, "adding tail call poke descriptor failed\n"); - goto out_free; - } - - func[i]->insnsi[insn_idx - subprog_start].imm = ret + 1; - - map_ptr = func[i]->aux->poke_tab[ret].tail_call.map; - ret = map_ptr->ops->map_poke_track(map_ptr, func[i]->aux); - if (ret < 0) { - verbose(env, "tracking tail call prog failed\n"); - goto out_free; - } + poke = &prog->aux->poke_tab[j]; + if (poke->insn_idx < subprog_end && + poke->insn_idx >= subprog_start) + poke->aux = func[i]->aux; } /* Use bpf_prog_F_tag to indicate functions in stack traces. @@ -12178,18 +12164,6 @@ static int jit_subprogs(struct bpf_verifier_env *env) cond_resched(); } - /* Untrack main program's aux structs so that during map_poke_run() - * we will not stumble upon the unfilled poke descriptors; each - * of the main program's poke descs got distributed across subprogs - * and got tracked onto map, so we are sure that none of them will - * be missed after the operation below - */ - for (i = 0; i < prog->aux->size_poke_tab; i++) { - map_ptr = prog->aux->poke_tab[i].tail_call.map; - - map_ptr->ops->map_poke_untrack(map_ptr, prog->aux); - } - /* at this point all bpf functions were successfully JITed * now populate all bpf_calls with correct addresses and * run last pass of JIT @@ -12267,14 +12241,22 @@ static int jit_subprogs(struct bpf_verifier_env *env) bpf_prog_jit_attempt_done(prog); return 0; out_free: + /* We failed JIT'ing, so at this point we need to unregister poke + * descriptors from subprogs, so that kernel is not attempting to + * patch it anymore as we're freeing the subprog JIT memory. + */ + for (i = 0; i < prog->aux->size_poke_tab; i++) { + map_ptr = prog->aux->poke_tab[i].tail_call.map; + map_ptr->ops->map_poke_untrack(map_ptr, prog->aux); + } + /* At this point we're guaranteed that poke descriptors are not + * live anymore. We can just unlink its descriptor table as it's + * released with the main prog. + */ for (i = 0; i < env->subprog_cnt; i++) { if (!func[i]) continue; - - for (j = 0; j < func[i]->aux->size_poke_tab; j++) { - map_ptr = func[i]->aux->poke_tab[j].tail_call.map; - map_ptr->ops->map_poke_untrack(map_ptr, func[i]->aux); - } + func[i]->aux->poke_tab = NULL; bpf_jit_free(func[i]); } kfree(func); -- cgit v1.3-14-g43fede From 1adee589cd6da2ead7f1b5dd82419eac59a2e2b0 Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Mon, 12 Jul 2021 11:03:35 -0500 Subject: kernel: debug: Fix unreachable code in gdb_serial_stub() Fix the following warning: kernel/debug/gdbstub.c:1049:4: warning: fallthrough annotation in unreachable code [-Wimplicit-fallthrough] fallthrough; ^ include/linux/compiler_attributes.h:210:41: note: expanded from macro 'fallthrough' # define fallthrough __attribute__((__fallthrough__) by placing the fallthrough; statement inside ifdeffery. Reported-by: kernel test robot Signed-off-by: Gustavo A. R. Silva --- kernel/debug/gdbstub.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/debug/gdbstub.c b/kernel/debug/gdbstub.c index 8372897402f4..b6f28fad4307 100644 --- a/kernel/debug/gdbstub.c +++ b/kernel/debug/gdbstub.c @@ -1045,8 +1045,8 @@ int gdb_serial_stub(struct kgdb_state *ks) gdb_cmd_detachkill(ks); return DBG_PASS_EVENT; } -#endif fallthrough; +#endif case 'C': /* Exception passing */ tmp = gdb_cmd_exception_pass(ks); if (tmp > 0) -- cgit v1.3-14-g43fede From e9ba16e68cce2f85e9f5d2eba5c0453f1a741fd2 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Sun, 11 Jul 2021 08:26:45 +0200 Subject: smpboot: Mark idle_init() as __always_inlined to work around aggressive compiler un-inlining While this function is a static inline, and is only used once in local scope, certain Kconfig variations may cause it to be compiled as a standalone function: 89231bf0 : 89231bf0: 83 05 60 d9 45 89 01 addl $0x1,0x8945d960 89231bf7: 55 push %ebp Resulting in this build failure: WARNING: modpost: vmlinux.o(.text.unlikely+0x7fd5): Section mismatch in reference from the function idle_init() to the function .init.text:fork_idle() The function idle_init() references the function __init fork_idle(). This is often because idle_init lacks a __init annotation or the annotation of fork_idle is wrong. ERROR: modpost: Section mismatches detected. Certain USBSAN options x86-32 builds with CONFIG_CC_OPTIMIZE_FOR_SIZE=y seem to be causing this. So mark idle_init() as __always_inline to work around this compiler bug/feature. Signed-off-by: Ingo Molnar --- kernel/smpboot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/smpboot.c b/kernel/smpboot.c index e4163042c4d6..21b7953f8242 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -47,7 +47,7 @@ void __init idle_thread_set_boot_cpu(void) * * Creates the thread if it does not exist. */ -static inline void idle_init(unsigned int cpu) +static inline void __always_inline idle_init(unsigned int cpu) { struct task_struct *tsk = per_cpu(idle_threads, cpu); -- cgit v1.3-14-g43fede From 5dd0a6b8582ffbfa88351949d50eccd5b6694ade Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Mon, 12 Jul 2021 22:57:35 +0200 Subject: bpf: Fix tail_call_reachable rejection for interpreter when jit failed During testing of f263a81451c1 ("bpf: Track subprog poke descriptors correctly and fix use-after-free") under various failure conditions, for example, when jit_subprogs() fails and tries to clean up the program to be run under the interpreter, we ran into the following freeze: [...] #127/8 tailcall_bpf2bpf_3:FAIL [...] [ 92.041251] BUG: KASAN: slab-out-of-bounds in ___bpf_prog_run+0x1b9d/0x2e20 [ 92.042408] Read of size 8 at addr ffff88800da67f68 by task test_progs/682 [ 92.043707] [ 92.044030] CPU: 1 PID: 682 Comm: test_progs Tainted: G O 5.13.0-53301-ge6c08cb33a30-dirty #87 [ 92.045542] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1 04/01/2014 [ 92.046785] Call Trace: [ 92.047171] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.047773] ? __bpf_prog_run_args32+0x8b/0xb0 [ 92.048389] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.049019] ? ktime_get+0x117/0x130 [...] // few hundred [similar] lines more [ 92.659025] ? ktime_get+0x117/0x130 [ 92.659845] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.660738] ? __bpf_prog_run_args32+0x8b/0xb0 [ 92.661528] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.662378] ? print_usage_bug+0x50/0x50 [ 92.663221] ? print_usage_bug+0x50/0x50 [ 92.664077] ? bpf_ksym_find+0x9c/0xe0 [ 92.664887] ? ktime_get+0x117/0x130 [ 92.665624] ? kernel_text_address+0xf5/0x100 [ 92.666529] ? __kernel_text_address+0xe/0x30 [ 92.667725] ? unwind_get_return_address+0x2f/0x50 [ 92.668854] ? ___bpf_prog_run+0x15d4/0x2e20 [ 92.670185] ? ktime_get+0x117/0x130 [ 92.671130] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.672020] ? __bpf_prog_run_args32+0x8b/0xb0 [ 92.672860] ? __bpf_prog_run_args64+0xc0/0xc0 [ 92.675159] ? ktime_get+0x117/0x130 [ 92.677074] ? lock_is_held_type+0xd5/0x130 [ 92.678662] ? ___bpf_prog_run+0x15d4/0x2e20 [ 92.680046] ? ktime_get+0x117/0x130 [ 92.681285] ? __bpf_prog_run32+0x6b/0x90 [ 92.682601] ? __bpf_prog_run64+0x90/0x90 [ 92.683636] ? lock_downgrade+0x370/0x370 [ 92.684647] ? mark_held_locks+0x44/0x90 [ 92.685652] ? ktime_get+0x117/0x130 [ 92.686752] ? lockdep_hardirqs_on+0x79/0x100 [ 92.688004] ? ktime_get+0x117/0x130 [ 92.688573] ? __cant_migrate+0x2b/0x80 [ 92.689192] ? bpf_test_run+0x2f4/0x510 [ 92.689869] ? bpf_test_timer_continue+0x1c0/0x1c0 [ 92.690856] ? rcu_read_lock_bh_held+0x90/0x90 [ 92.691506] ? __kasan_slab_alloc+0x61/0x80 [ 92.692128] ? eth_type_trans+0x128/0x240 [ 92.692737] ? __build_skb+0x46/0x50 [ 92.693252] ? bpf_prog_test_run_skb+0x65e/0xc50 [ 92.693954] ? bpf_prog_test_run_raw_tp+0x2d0/0x2d0 [ 92.694639] ? __fget_light+0xa1/0x100 [ 92.695162] ? bpf_prog_inc+0x23/0x30 [ 92.695685] ? __sys_bpf+0xb40/0x2c80 [ 92.696324] ? bpf_link_get_from_fd+0x90/0x90 [ 92.697150] ? mark_held_locks+0x24/0x90 [ 92.698007] ? lockdep_hardirqs_on_prepare+0x124/0x220 [ 92.699045] ? finish_task_switch+0xe6/0x370 [ 92.700072] ? lockdep_hardirqs_on+0x79/0x100 [ 92.701233] ? finish_task_switch+0x11d/0x370 [ 92.702264] ? __switch_to+0x2c0/0x740 [ 92.703148] ? mark_held_locks+0x24/0x90 [ 92.704155] ? __x64_sys_bpf+0x45/0x50 [ 92.705146] ? do_syscall_64+0x35/0x80 [ 92.706953] ? entry_SYSCALL_64_after_hwframe+0x44/0xae [...] Turns out that the program rejection from e411901c0b77 ("bpf: allow for tailcalls in BPF subprograms for x64 JIT") is buggy since env->prog->aux->tail_call_reachable is never true. Commit ebf7d1f508a7 ("bpf, x64: rework pro/epilogue and tailcall handling in JIT") added a tracker into check_max_stack_depth() which propagates the tail_call_reachable condition throughout the subprograms. This info is then assigned to the subprogram's func[i]->aux->tail_call_reachable. However, in the case of the rejection check upon JIT failure, env->prog->aux->tail_call_reachable is used. func[0]->aux->tail_call_reachable which represents the main program's information did not propagate this to the outer env->prog->aux, though. Add this propagation into check_max_stack_depth() where it needs to belong so that the check can be done reliably. Fixes: ebf7d1f508a7 ("bpf, x64: rework pro/epilogue and tailcall handling in JIT") Fixes: e411901c0b77 ("bpf: allow for tailcalls in BPF subprograms for x64 JIT") Co-developed-by: John Fastabend Signed-off-by: Daniel Borkmann Signed-off-by: John Fastabend Signed-off-by: Alexei Starovoitov Acked-by: Maciej Fijalkowski Link: https://lore.kernel.org/bpf/618c34e3163ad1a36b1e82377576a6081e182f25.1626123173.git.daniel@iogearbox.net --- kernel/bpf/verifier.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 42a4063de7cd..9de3c9c3267c 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -3677,6 +3677,8 @@ continue_func: if (tail_call_reachable) for (j = 0; j < frame; j++) subprog[ret_prog[j]].tail_call_reachable = true; + if (subprog[0].tail_call_reachable) + env->prog->aux->tail_call_reachable = true; /* end of for() loop means the last insn of the 'subprog' * was reached. Doesn't matter whether it was JA or EXIT -- cgit v1.3-14-g43fede From 3b0462726e7ef281c35a7a4ae33e93ee2bc9975b Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 14 Jul 2021 15:47:49 +0200 Subject: cgroup: verify that source is a string The following sequence can be used to trigger a UAF: int fscontext_fd = fsopen("cgroup"); int fd_null = open("/dev/null, O_RDONLY); int fsconfig(fscontext_fd, FSCONFIG_SET_FD, "source", fd_null); close_range(3, ~0U, 0); The cgroup v1 specific fs parser expects a string for the "source" parameter. However, it is perfectly legitimate to e.g. specify a file descriptor for the "source" parameter. The fs parser doesn't know what a filesystem allows there. So it's a bug to assume that "source" is always of type fs_value_is_string when it can reasonably also be fs_value_is_file. This assumption in the cgroup code causes a UAF because struct fs_parameter uses a union for the actual value. Access to that union is guarded by the param->type member. Since the cgroup paramter parser didn't check param->type but unconditionally moved param->string into fc->source a close on the fscontext_fd would trigger a UAF during put_fs_context() which frees fc->source thereby freeing the file stashed in param->file causing a UAF during a close of the fd_null. Fix this by verifying that param->type is actually a string and report an error if not. In follow up patches I'll add a new generic helper that can be used here and by other filesystems instead of this error-prone copy-pasta fix. But fixing it in here first makes backporting a it to stable a lot easier. Fixes: 8d2451f4994f ("cgroup1: switch to option-by-option parsing") Reported-by: syzbot+283ce5a46486d6acdbaf@syzkaller.appspotmail.com Cc: Christoph Hellwig Cc: Alexander Viro Cc: Dmitry Vyukov Cc: Cc: syzkaller-bugs Signed-off-by: Christian Brauner Signed-off-by: Linus Torvalds --- kernel/cgroup/cgroup-v1.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'kernel') diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index ee93b6e89587..527917c0b30b 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -912,6 +912,8 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) opt = fs_parse(fc, cgroup1_fs_parameters, param, &result); if (opt == -ENOPARAM) { if (strcmp(param->key, "source") == 0) { + if (param->type != fs_value_is_string) + return invalf(fc, "Non-string source"); if (fc->source) return invalf(fc, "Multiple sources not supported"); fc->source = param->string; -- cgit v1.3-14-g43fede From d1d488d813703618f0dd93f0e4c4a05928114aa8 Mon Sep 17 00:00:00 2001 From: Christian Brauner Date: Wed, 14 Jul 2021 15:47:50 +0200 Subject: fs: add vfs_parse_fs_param_source() helper Add a simple helper that filesystems can use in their parameter parser to parse the "source" parameter. A few places open-coded this function and that already caused a bug in the cgroup v1 parser that we fixed. Let's make it harder to get this wrong by introducing a helper which performs all necessary checks. Link: https://syzkaller.appspot.com/bug?id=6312526aba5beae046fdae8f00399f87aab48b12 Cc: Christoph Hellwig Cc: Alexander Viro Cc: Dmitry Vyukov Signed-off-by: Christian Brauner Signed-off-by: Linus Torvalds --- fs/fs_context.c | 54 ++++++++++++++++++++++++++++++---------------- include/linux/fs_context.h | 2 ++ kernel/cgroup/cgroup-v1.c | 14 +++++------- 3 files changed, 43 insertions(+), 27 deletions(-) (limited to 'kernel') diff --git a/fs/fs_context.c b/fs/fs_context.c index 2834d1afa6e8..de1985eae535 100644 --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -79,6 +79,35 @@ static int vfs_parse_sb_flag(struct fs_context *fc, const char *key) return -ENOPARAM; } +/** + * vfs_parse_fs_param_source - Handle setting "source" via parameter + * @fc: The filesystem context to modify + * @param: The parameter + * + * This is a simple helper for filesystems to verify that the "source" they + * accept is sane. + * + * Returns 0 on success, -ENOPARAM if this is not "source" parameter, and + * -EINVAL otherwise. In the event of failure, supplementary error information + * is logged. + */ +int vfs_parse_fs_param_source(struct fs_context *fc, struct fs_parameter *param) +{ + if (strcmp(param->key, "source") != 0) + return -ENOPARAM; + + if (param->type != fs_value_is_string) + return invalf(fc, "Non-string source"); + + if (fc->source) + return invalf(fc, "Multiple sources"); + + fc->source = param->string; + param->string = NULL; + return 0; +} +EXPORT_SYMBOL(vfs_parse_fs_param_source); + /** * vfs_parse_fs_param - Add a single parameter to a superblock config * @fc: The filesystem context to modify @@ -122,15 +151,9 @@ int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param) /* If the filesystem doesn't take any arguments, give it the * default handling of source. */ - if (strcmp(param->key, "source") == 0) { - if (param->type != fs_value_is_string) - return invalf(fc, "VFS: Non-string source"); - if (fc->source) - return invalf(fc, "VFS: Multiple sources"); - fc->source = param->string; - param->string = NULL; - return 0; - } + ret = vfs_parse_fs_param_source(fc, param); + if (ret != -ENOPARAM) + return ret; return invalf(fc, "%s: Unknown parameter '%s'", fc->fs_type->name, param->key); @@ -504,16 +527,11 @@ static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param) struct legacy_fs_context *ctx = fc->fs_private; unsigned int size = ctx->data_size; size_t len = 0; + int ret; - if (strcmp(param->key, "source") == 0) { - if (param->type != fs_value_is_string) - return invalf(fc, "VFS: Legacy: Non-string source"); - if (fc->source) - return invalf(fc, "VFS: Legacy: Multiple sources"); - fc->source = param->string; - param->string = NULL; - return 0; - } + ret = vfs_parse_fs_param_source(fc, param); + if (ret != -ENOPARAM) + return ret; if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS) return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options"); diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index 37e1e8f7f08d..e2bc16300c82 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -139,6 +139,8 @@ extern int vfs_parse_fs_string(struct fs_context *fc, const char *key, extern int generic_parse_monolithic(struct fs_context *fc, void *data); extern int vfs_get_tree(struct fs_context *fc); extern void put_fs_context(struct fs_context *fc); +extern int vfs_parse_fs_param_source(struct fs_context *fc, + struct fs_parameter *param); /* * sget() wrappers to be called from the ->get_tree() op. diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 527917c0b30b..8d6bf56ed77a 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -911,15 +911,11 @@ int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param) opt = fs_parse(fc, cgroup1_fs_parameters, param, &result); if (opt == -ENOPARAM) { - if (strcmp(param->key, "source") == 0) { - if (param->type != fs_value_is_string) - return invalf(fc, "Non-string source"); - if (fc->source) - return invalf(fc, "Multiple sources not supported"); - fc->source = param->string; - param->string = NULL; - return 0; - } + int ret; + + ret = vfs_parse_fs_param_source(fc, param); + if (ret != -ENOPARAM) + return ret; for_each_subsys(ss, i) { if (strcmp(param->key, ss->legacy_name)) continue; -- cgit v1.3-14-g43fede From 1a3402d93c73bf6bb4df6d7c2aac35abfc3c50e2 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Thu, 3 Jun 2021 01:15:59 +0200 Subject: posix-cpu-timers: Fix rearm racing against process tick Since the process wide cputime counter is started locklessly from posix_cpu_timer_rearm(), it can be concurrently stopped by operations on other timers from the same thread group, such as in the following unlucky scenario: CPU 0 CPU 1 ----- ----- timer_settime(TIMER B) posix_cpu_timer_rearm(TIMER A) cpu_clock_sample_group() (pct->timers_active already true) handle_posix_cpu_timers() check_process_timers() stop_process_timers() pct->timers_active = false arm_timer(TIMER A) tick -> run_posix_cpu_timers() // sees !pct->timers_active, ignore // our TIMER A Fix this with simply locking process wide cputime counting start and timer arm in the same block. Acked-by: Peter Zijlstra (Intel) Signed-off-by: Frederic Weisbecker Fixes: 60f2ceaa8111 ("posix-cpu-timers: Remove unnecessary locking around cpu_clock_sample_group") Cc: stable@vger.kernel.org Cc: Oleg Nesterov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Eric W. Biederman --- kernel/time/posix-cpu-timers.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index 29a5e54e6e10..517be7fd175e 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -991,6 +991,11 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) if (!p) goto out; + /* Protect timer list r/w in arm_timer() */ + sighand = lock_task_sighand(p, &flags); + if (unlikely(sighand == NULL)) + goto out; + /* * Fetch the current sample and update the timer's expiry time. */ @@ -1001,11 +1006,6 @@ static void posix_cpu_timer_rearm(struct k_itimer *timer) bump_cpu_timer(timer, now); - /* Protect timer list r/w in arm_timer() */ - sighand = lock_task_sighand(p, &flags); - if (unlikely(sighand == NULL)) - goto out; - /* * Now re-arm for the new expiry time. */ -- cgit v1.3-14-g43fede From aebacb7f6ca1926918734faae14d1f0b6fae5cb7 Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Fri, 9 Jul 2021 16:13:25 +0200 Subject: timers: Fix get_next_timer_interrupt() with no timers pending 31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") subtly altered get_next_timer_interrupt()'s behaviour. The function no longer consistently returns KTIME_MAX with no timers pending. In order to decide if there are any timers pending we check whether the next expiry will happen NEXT_TIMER_MAX_DELTA jiffies from now. Unfortunately, the next expiry time and the timer base clock are no longer updated in unison. The former changes upon certain timer operations (enqueue, expire, detach), whereas the latter keeps track of jiffies as they move forward. Ultimately breaking the logic above. A simplified example: - Upon entering get_next_timer_interrupt() with: jiffies = 1 base->clk = 0; base->next_expiry = NEXT_TIMER_MAX_DELTA; 'base->next_expiry == base->clk + NEXT_TIMER_MAX_DELTA', the function returns KTIME_MAX. - 'base->clk' is updated to the jiffies value. - The next time we enter get_next_timer_interrupt(), taking into account no timer operations happened: base->clk = 1; base->next_expiry = NEXT_TIMER_MAX_DELTA; 'base->next_expiry != base->clk + NEXT_TIMER_MAX_DELTA', the function returns a valid expire time, which is incorrect. This ultimately might unnecessarily rearm sched's timer on nohz_full setups, and add latency to the system[1]. So, introduce 'base->timers_pending'[2], update it every time 'base->next_expiry' changes, and use it in get_next_timer_interrupt(). [1] See tick_nohz_stop_tick(). [2] A quick pahole check on x86_64 and arm64 shows it doesn't make 'struct timer_base' any bigger. Fixes: 31cd0e119d50 ("timers: Recalculate next timer interrupt only when necessary") Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Frederic Weisbecker --- kernel/time/timer.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/time/timer.c b/kernel/time/timer.c index 3fadb58fc9d7..9eb11c2209e5 100644 --- a/kernel/time/timer.c +++ b/kernel/time/timer.c @@ -207,6 +207,7 @@ struct timer_base { unsigned int cpu; bool next_expiry_recalc; bool is_idle; + bool timers_pending; DECLARE_BITMAP(pending_map, WHEEL_SIZE); struct hlist_head vectors[WHEEL_SIZE]; } ____cacheline_aligned; @@ -595,6 +596,7 @@ static void enqueue_timer(struct timer_base *base, struct timer_list *timer, * can reevaluate the wheel: */ base->next_expiry = bucket_expiry; + base->timers_pending = true; base->next_expiry_recalc = false; trigger_dyntick_cpu(base, timer); } @@ -1582,6 +1584,7 @@ static unsigned long __next_timer_interrupt(struct timer_base *base) } base->next_expiry_recalc = false; + base->timers_pending = !(next == base->clk + NEXT_TIMER_MAX_DELTA); return next; } @@ -1633,7 +1636,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) struct timer_base *base = this_cpu_ptr(&timer_bases[BASE_STD]); u64 expires = KTIME_MAX; unsigned long nextevt; - bool is_max_delta; /* * Pretend that there is no timer pending if the cpu is offline. @@ -1646,7 +1648,6 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) if (base->next_expiry_recalc) base->next_expiry = __next_timer_interrupt(base); nextevt = base->next_expiry; - is_max_delta = (nextevt == base->clk + NEXT_TIMER_MAX_DELTA); /* * We have a fresh next event. Check whether we can forward the @@ -1664,7 +1665,7 @@ u64 get_next_timer_interrupt(unsigned long basej, u64 basem) expires = basem; base->is_idle = false; } else { - if (!is_max_delta) + if (base->timers_pending) expires = basem + (u64)(nextevt - basej) * TICK_NSEC; /* * If we expect to sleep more than a tick, mark the base idle. @@ -1947,6 +1948,7 @@ int timers_prepare_cpu(unsigned int cpu) base = per_cpu_ptr(&timer_bases[b], cpu); base->clk = jiffies; base->next_expiry = base->clk + NEXT_TIMER_MAX_DELTA; + base->timers_pending = false; base->is_idle = false; } return 0; -- cgit v1.3-14-g43fede From 704adfb5a9978462cd861f170201ae2b5e3d3a80 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 15 Jul 2021 00:02:06 -0400 Subject: tracing: Do not reference char * as a string in histograms The histogram logic was allowing events with char * pointers to be used as normal strings. But it was easy to crash the kernel with: # echo 'hist:keys=filename' > events/syscalls/sys_enter_openat/trigger And open some files, and boom! BUG: unable to handle page fault for address: 00007f2ced0c3280 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 1173fa067 P4D 1173fa067 PUD 1171b6067 PMD 1171dd067 PTE 0 Oops: 0000 [#1] PREEMPT SMP CPU: 6 PID: 1810 Comm: cat Not tainted 5.13.0-rc5-test+ #61 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 RIP: 0010:strlen+0x0/0x20 Code: f6 82 80 2a 0b a9 20 74 11 0f b6 50 01 48 83 c0 01 f6 82 80 2a 0b a9 20 75 ef c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 00 75 f7 48 29 f8 c3 RSP: 0018:ffffbdbf81567b50 EFLAGS: 00010246 RAX: 0000000000000003 RBX: ffff93815cdb3800 RCX: ffff9382401a22d0 RDX: 0000000000000100 RSI: 0000000000000000 RDI: 00007f2ced0c3280 RBP: 0000000000000100 R08: ffff9382409ff074 R09: ffffbdbf81567c98 R10: ffff9382409ff074 R11: 0000000000000000 R12: ffff9382409ff074 R13: 0000000000000001 R14: ffff93815a744f00 R15: 00007f2ced0c3280 FS: 00007f2ced0f8580(0000) GS:ffff93825a800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f2ced0c3280 CR3: 0000000107069005 CR4: 00000000001706e0 Call Trace: event_hist_trigger+0x463/0x5f0 ? find_held_lock+0x32/0x90 ? sched_clock_cpu+0xe/0xd0 ? lock_release+0x155/0x440 ? kernel_init_free_pages+0x6d/0x90 ? preempt_count_sub+0x9b/0xd0 ? kernel_init_free_pages+0x6d/0x90 ? get_page_from_freelist+0x12c4/0x1680 ? __rb_reserve_next+0xe5/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 event_triggers_call+0x52/0xe0 ftrace_syscall_enter+0x264/0x2c0 syscall_trace_enter.constprop.0+0x1ee/0x210 do_syscall_64+0x1c/0x80 entry_SYSCALL_64_after_hwframe+0x44/0xae Where it triggered a fault on strlen(key) where key was the filename. The reason is that filename is a char * to user space, and the histogram code just blindly dereferenced it, with obvious bad results. I originally tried to use strncpy_from_user/kernel_nofault() but found that there's other places that its dereferenced and not worth the effort. Just do not allow "char *" to act like strings. Link: https://lkml.kernel.org/r/20210715000206.025df9d2@rorschach.local.home Cc: Ingo Molnar Cc: Andrew Morton Cc: Masami Hiramatsu Cc: Tzvetomir Stoyanov Cc: stable@vger.kernel.org Acked-by: Namhyung Kim Acked-by: Tom Zanussi Fixes: 79e577cbce4c4 ("tracing: Support string type key properly") Fixes: 5967bd5c4239 ("tracing: Let filter_assign_type() detect FILTER_PTR_STRING") Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_hist.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 0207aeed31e6..16a9dfc9fffc 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1689,7 +1689,9 @@ static struct hist_field *create_hist_field(struct hist_trigger_data *hist_data, if (WARN_ON_ONCE(!field)) goto out; - if (is_string_field(field)) { + /* Pointers to strings are just pointers and dangerous to dereference */ + if (is_string_field(field) && + (field->filter_type != FILTER_PTR_STRING)) { flags |= HIST_FIELD_FL_STRING; hist_field->size = MAX_FILTER_STR_VAL; @@ -4495,8 +4497,6 @@ static inline void add_to_key(char *compound_key, void *key, field = key_field->field; if (field->filter_type == FILTER_DYN_STRING) size = *(u32 *)(rec + field->offset) >> 16; - else if (field->filter_type == FILTER_PTR_STRING) - size = strlen(key); else if (field->filter_type == FILTER_STATIC_STRING) size = field->size; -- cgit v1.3-14-g43fede From 40ac971eab89330d6153e7721e88acd2d98833f9 Mon Sep 17 00:00:00 2001 From: Roman Skakun Date: Fri, 16 Jul 2021 11:39:34 +0300 Subject: dma-mapping: handle vmalloc addresses in dma_common_{mmap,get_sgtable} xen-swiotlb can use vmalloc backed addresses for dma coherent allocations and uses the common helpers. Properly handle them to unbreak Xen on ARM platforms. Fixes: 1b65c4e5a9af ("swiotlb-xen: use xen_alloc/free_coherent_pages") Signed-off-by: Roman Skakun Reviewed-by: Andrii Anisov [hch: split the patch, renamed the helpers] Signed-off-by: Christoph Hellwig --- kernel/dma/ops_helpers.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'kernel') diff --git a/kernel/dma/ops_helpers.c b/kernel/dma/ops_helpers.c index 910ae69cae77..af4a6ef48ce0 100644 --- a/kernel/dma/ops_helpers.c +++ b/kernel/dma/ops_helpers.c @@ -5,6 +5,13 @@ */ #include +static struct page *dma_common_vaddr_to_page(void *cpu_addr) +{ + if (is_vmalloc_addr(cpu_addr)) + return vmalloc_to_page(cpu_addr); + return virt_to_page(cpu_addr); +} + /* * Create scatter-list for the already allocated DMA buffer. */ @@ -12,7 +19,7 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt, void *cpu_addr, dma_addr_t dma_addr, size_t size, unsigned long attrs) { - struct page *page = virt_to_page(cpu_addr); + struct page *page = dma_common_vaddr_to_page(cpu_addr); int ret; ret = sg_alloc_table(sgt, 1, GFP_KERNEL); @@ -32,6 +39,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, unsigned long user_count = vma_pages(vma); unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT; unsigned long off = vma->vm_pgoff; + struct page *page = dma_common_vaddr_to_page(cpu_addr); int ret = -ENXIO; vma->vm_page_prot = dma_pgprot(dev, vma->vm_page_prot, attrs); @@ -43,7 +51,7 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma, return -ENXIO; return remap_pfn_range(vma, vma->vm_start, - page_to_pfn(virt_to_page(cpu_addr)) + vma->vm_pgoff, + page_to_pfn(page) + vma->vm_pgoff, user_count << PAGE_SHIFT, vma->vm_page_prot); #else return -ENXIO; -- cgit v1.3-14-g43fede From 59089a189e3adde4cf85f2ce479738d1ae4c514d Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 29 Jun 2021 09:39:15 +0000 Subject: bpf: Remove superfluous aux sanitation on subprog rejection Follow-up to fe9a5ca7e370 ("bpf: Do not mark insn as seen under speculative path verification"). The sanitize_insn_aux_data() helper does not serve a particular purpose in today's code. The original intention for the helper was that if function-by-function verification fails, a given program would be cleared from temporary insn_aux_data[], and then its verification would be re-attempted in the context of the main program a second time. However, a failure in do_check_subprogs() will skip do_check_main() and propagate the error to the user instead, thus such situation can never occur. Given its interaction is not compatible to the Spectre v1 mitigation (due to comparing aux->seen with env->pass_cnt), just remove sanitize_insn_aux_data() to avoid future bugs in this area. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 34 ---------------------------------- 1 file changed, 34 deletions(-) (limited to 'kernel') diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 9de3c9c3267c..8a7a28b4cfb9 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12752,37 +12752,6 @@ static void free_states(struct bpf_verifier_env *env) } } -/* The verifier is using insn_aux_data[] to store temporary data during - * verification and to store information for passes that run after the - * verification like dead code sanitization. do_check_common() for subprogram N - * may analyze many other subprograms. sanitize_insn_aux_data() clears all - * temporary data after do_check_common() finds that subprogram N cannot be - * verified independently. pass_cnt counts the number of times - * do_check_common() was run and insn->aux->seen tells the pass number - * insn_aux_data was touched. These variables are compared to clear temporary - * data from failed pass. For testing and experiments do_check_common() can be - * run multiple times even when prior attempt to verify is unsuccessful. - * - * Note that special handling is needed on !env->bypass_spec_v1 if this is - * ever called outside of error path with subsequent program rejection. - */ -static void sanitize_insn_aux_data(struct bpf_verifier_env *env) -{ - struct bpf_insn *insn = env->prog->insnsi; - struct bpf_insn_aux_data *aux; - int i, class; - - for (i = 0; i < env->prog->len; i++) { - class = BPF_CLASS(insn[i].code); - if (class != BPF_LDX && class != BPF_STX) - continue; - aux = &env->insn_aux_data[i]; - if (aux->seen != env->pass_cnt) - continue; - memset(aux, 0, offsetof(typeof(*aux), orig_idx)); - } -} - static int do_check_common(struct bpf_verifier_env *env, int subprog) { bool pop_log = !(env->log.level & BPF_LOG_LEVEL2); @@ -12859,9 +12828,6 @@ out: if (!ret && pop_log) bpf_vlog_reset(&env->log, 0); free_states(env); - if (ret) - /* clean aux data in case subprog was rejected */ - sanitize_insn_aux_data(env); return ret; } -- cgit v1.3-14-g43fede From e042aa532c84d18ff13291d00620502ce7a38dda Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Fri, 16 Jul 2021 09:18:21 +0000 Subject: bpf: Fix pointer arithmetic mask tightening under state pruning In 7fedb63a8307 ("bpf: Tighten speculative pointer arithmetic mask") we narrowed the offset mask for unprivileged pointer arithmetic in order to mitigate a corner case where in the speculative domain it is possible to advance, for example, the map value pointer by up to value_size-1 out-of- bounds in order to leak kernel memory via side-channel to user space. The verifier's state pruning for scalars leaves one corner case open where in the first verification path R_x holds an unknown scalar with an aux->alu_limit of e.g. 7, and in a second verification path that same register R_x, here denoted as R_x', holds an unknown scalar which has tighter bounds and would thus satisfy range_within(R_x, R_x') as well as tnum_in(R_x, R_x') for state pruning, yielding an aux->alu_limit of 3: Given the second path fits the register constraints for pruning, the final generated mask from aux->alu_limit will remain at 7. While technically not wrong for the non-speculative domain, it would however be possible to craft similar cases where the mask would be too wide as in 7fedb63a8307. One way to fix it is to detect the presence of unknown scalar map pointer arithmetic and force a deeper search on unknown scalars to ensure that we do not run into a masking mismatch. Signed-off-by: Daniel Borkmann Acked-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 27 +++++++++++++++++---------- 2 files changed, 18 insertions(+), 10 deletions(-) (limited to 'kernel') diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index e774ecc1cd1f..7ba7e800d472 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -414,6 +414,7 @@ struct bpf_verifier_env { u32 used_map_cnt; /* number of used maps */ u32 used_btf_cnt; /* number of used BTF objects */ u32 id_gen; /* used to generate unique reg IDs */ + bool explore_alu_limits; bool allow_ptr_leaks; bool allow_uninit_stack; bool allow_ptr_to_map_access; diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 8a7a28b4cfb9..657062cb4d85 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -6561,6 +6561,12 @@ static int sanitize_ptr_alu(struct bpf_verifier_env *env, alu_state |= off_is_imm ? BPF_ALU_IMMEDIATE : 0; alu_state |= ptr_is_dst_reg ? BPF_ALU_SANITIZE_SRC : BPF_ALU_SANITIZE_DST; + + /* Limit pruning on unknown scalars to enable deep search for + * potential masking differences from other program paths. + */ + if (!off_is_imm) + env->explore_alu_limits = true; } err = update_alu_sanitation_state(aux, alu_state, alu_limit); @@ -9936,8 +9942,8 @@ next: } /* Returns true if (rold safe implies rcur safe) */ -static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur, - struct bpf_id_pair *idmap) +static bool regsafe(struct bpf_verifier_env *env, struct bpf_reg_state *rold, + struct bpf_reg_state *rcur, struct bpf_id_pair *idmap) { bool equal; @@ -9963,6 +9969,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur, return false; switch (rold->type) { case SCALAR_VALUE: + if (env->explore_alu_limits) + return false; if (rcur->type == SCALAR_VALUE) { if (!rold->precise && !rcur->precise) return true; @@ -10053,9 +10061,8 @@ static bool regsafe(struct bpf_reg_state *rold, struct bpf_reg_state *rcur, return false; } -static bool stacksafe(struct bpf_func_state *old, - struct bpf_func_state *cur, - struct bpf_id_pair *idmap) +static bool stacksafe(struct bpf_verifier_env *env, struct bpf_func_state *old, + struct bpf_func_state *cur, struct bpf_id_pair *idmap) { int i, spi; @@ -10100,9 +10107,8 @@ static bool stacksafe(struct bpf_func_state *old, continue; if (old->stack[spi].slot_type[0] != STACK_SPILL) continue; - if (!regsafe(&old->stack[spi].spilled_ptr, - &cur->stack[spi].spilled_ptr, - idmap)) + if (!regsafe(env, &old->stack[spi].spilled_ptr, + &cur->stack[spi].spilled_ptr, idmap)) /* when explored and current stack slot are both storing * spilled registers, check that stored pointers types * are the same as well. @@ -10159,10 +10165,11 @@ static bool func_states_equal(struct bpf_verifier_env *env, struct bpf_func_stat memset(env->idmap_scratch, 0, sizeof(env->idmap_scratch)); for (i = 0; i < MAX_BPF_REG; i++) - if (!regsafe(&old->regs[i], &cur->regs[i], env->idmap_scratch)) + if (!regsafe(env, &old->regs[i], &cur->regs[i], + env->idmap_scratch)) return false; - if (!stacksafe(old, cur, env->idmap_scratch)) + if (!stacksafe(env, old, cur, env->idmap_scratch)) return false; if (!refsafe(old, cur)) -- cgit v1.3-14-g43fede From 1e7107c5ef44431bc1ebbd4c353f1d7c22e5f2ec Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Wed, 16 Jun 2021 08:51:57 -0400 Subject: cgroup1: fix leaked context root causing sporadic NULL deref in LTP MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Richard reported sporadic (roughly one in 10 or so) null dereferences and other strange behaviour for a set of automated LTP tests. Things like: BUG: kernel NULL pointer dereference, address: 0000000000000008 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP PTI CPU: 0 PID: 1516 Comm: umount Not tainted 5.10.0-yocto-standard #1 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-48-gd9c812dda519-prebuilt.qemu.org 04/01/2014 RIP: 0010:kernfs_sop_show_path+0x1b/0x60 ...or these others: RIP: 0010:do_mkdirat+0x6a/0xf0 RIP: 0010:d_alloc_parallel+0x98/0x510 RIP: 0010:do_readlinkat+0x86/0x120 There were other less common instances of some kind of a general scribble but the common theme was mount and cgroup and a dubious dentry triggering the NULL dereference. I was only able to reproduce it under qemu by replicating Richard's setup as closely as possible - I never did get it to happen on bare metal, even while keeping everything else the same. In commit 71d883c37e8d ("cgroup_do_mount(): massage calling conventions") we see this as a part of the overall change: -------------- struct cgroup_subsys *ss; - struct dentry *dentry; [...] - dentry = cgroup_do_mount(&cgroup_fs_type, fc->sb_flags, root, - CGROUP_SUPER_MAGIC, ns); [...] - if (percpu_ref_is_dying(&root->cgrp.self.refcnt)) { - struct super_block *sb = dentry->d_sb; - dput(dentry); + ret = cgroup_do_mount(fc, CGROUP_SUPER_MAGIC, ns); + if (!ret && percpu_ref_is_dying(&root->cgrp.self.refcnt)) { + struct super_block *sb = fc->root->d_sb; + dput(fc->root); deactivate_locked_super(sb); msleep(10); return restart_syscall(); } -------------- In changing from the local "*dentry" variable to using fc->root, we now export/leave that dentry pointer in the file context after doing the dput() in the unlikely "is_dying" case. With LTP doing a crazy amount of back to back mount/unmount [testcases/bin/cgroup_regression_5_1.sh] the unlikely becomes slightly likely and then bad things happen. A fix would be to not leave the stale reference in fc->root as follows: --------------                 dput(fc->root); + fc->root = NULL;                 deactivate_locked_super(sb); -------------- ...but then we are just open-coding a duplicate of fc_drop_locked() so we simply use that instead. Cc: Al Viro Cc: Tejun Heo Cc: Zefan Li Cc: Johannes Weiner Cc: stable@vger.kernel.org # v5.1+ Reported-by: Richard Purdie Fixes: 71d883c37e8d ("cgroup_do_mount(): massage calling conventions") Signed-off-by: Paul Gortmaker Signed-off-by: Tejun Heo --- fs/internal.h | 1 - include/linux/fs_context.h | 1 + kernel/cgroup/cgroup-v1.c | 4 +--- 3 files changed, 2 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/fs/internal.h b/fs/internal.h index 3ce8edbaa3ca..82e8eb32ff3d 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -61,7 +61,6 @@ extern void __init chrdev_init(void); */ extern const struct fs_context_operations legacy_fs_context_ops; extern int parse_monolithic_mount_data(struct fs_context *, void *); -extern void fc_drop_locked(struct fs_context *); extern void vfs_clean_context(struct fs_context *fc); extern int finish_clean_context(struct fs_context *fc); diff --git a/include/linux/fs_context.h b/include/linux/fs_context.h index e2bc16300c82..6b54982fc5f3 100644 --- a/include/linux/fs_context.h +++ b/include/linux/fs_context.h @@ -141,6 +141,7 @@ extern int vfs_get_tree(struct fs_context *fc); extern void put_fs_context(struct fs_context *fc); extern int vfs_parse_fs_param_source(struct fs_context *fc, struct fs_parameter *param); +extern void fc_drop_locked(struct fs_context *fc); /* * sget() wrappers to be called from the ->get_tree() op. diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 8d6bf56ed77a..de2c432dee20 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -1221,9 +1221,7 @@ int cgroup1_get_tree(struct fs_context *fc) ret = cgroup_do_get_tree(fc); if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) { - struct super_block *sb = fc->root->d_sb; - dput(fc->root); - deactivate_locked_super(sb); + fc_drop_locked(fc); ret = 1; } -- cgit v1.3-14-g43fede From b42b0bddcbc87b4c66f6497f66fc72d52b712aa7 Mon Sep 17 00:00:00 2001 From: Yang Yingliang Date: Wed, 14 Jul 2021 17:19:33 +0800 Subject: workqueue: fix UAF in pwq_unbound_release_workfn() I got a UAF report when doing fuzz test: [ 152.880091][ T8030] ================================================================== [ 152.881240][ T8030] BUG: KASAN: use-after-free in pwq_unbound_release_workfn+0x50/0x190 [ 152.882442][ T8030] Read of size 4 at addr ffff88810d31bd00 by task kworker/3:2/8030 [ 152.883578][ T8030] [ 152.883932][ T8030] CPU: 3 PID: 8030 Comm: kworker/3:2 Not tainted 5.13.0+ #249 [ 152.885014][ T8030] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 [ 152.886442][ T8030] Workqueue: events pwq_unbound_release_workfn [ 152.887358][ T8030] Call Trace: [ 152.887837][ T8030] dump_stack_lvl+0x75/0x9b [ 152.888525][ T8030] ? pwq_unbound_release_workfn+0x50/0x190 [ 152.889371][ T8030] print_address_description.constprop.10+0x48/0x70 [ 152.890326][ T8030] ? pwq_unbound_release_workfn+0x50/0x190 [ 152.891163][ T8030] ? pwq_unbound_release_workfn+0x50/0x190 [ 152.891999][ T8030] kasan_report.cold.15+0x82/0xdb [ 152.892740][ T8030] ? pwq_unbound_release_workfn+0x50/0x190 [ 152.893594][ T8030] __asan_load4+0x69/0x90 [ 152.894243][ T8030] pwq_unbound_release_workfn+0x50/0x190 [ 152.895057][ T8030] process_one_work+0x47b/0x890 [ 152.895778][ T8030] worker_thread+0x5c/0x790 [ 152.896439][ T8030] ? process_one_work+0x890/0x890 [ 152.897163][ T8030] kthread+0x223/0x250 [ 152.897747][ T8030] ? set_kthread_struct+0xb0/0xb0 [ 152.898471][ T8030] ret_from_fork+0x1f/0x30 [ 152.899114][ T8030] [ 152.899446][ T8030] Allocated by task 8884: [ 152.900084][ T8030] kasan_save_stack+0x21/0x50 [ 152.900769][ T8030] __kasan_kmalloc+0x88/0xb0 [ 152.901416][ T8030] __kmalloc+0x29c/0x460 [ 152.902014][ T8030] alloc_workqueue+0x111/0x8e0 [ 152.902690][ T8030] __btrfs_alloc_workqueue+0x11e/0x2a0 [ 152.903459][ T8030] btrfs_alloc_workqueue+0x6d/0x1d0 [ 152.904198][ T8030] scrub_workers_get+0x1e8/0x490 [ 152.904929][ T8030] btrfs_scrub_dev+0x1b9/0x9c0 [ 152.905599][ T8030] btrfs_ioctl+0x122c/0x4e50 [ 152.906247][ T8030] __x64_sys_ioctl+0x137/0x190 [ 152.906916][ T8030] do_syscall_64+0x34/0xb0 [ 152.907535][ T8030] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 152.908365][ T8030] [ 152.908688][ T8030] Freed by task 8884: [ 152.909243][ T8030] kasan_save_stack+0x21/0x50 [ 152.909893][ T8030] kasan_set_track+0x20/0x30 [ 152.910541][ T8030] kasan_set_free_info+0x24/0x40 [ 152.911265][ T8030] __kasan_slab_free+0xf7/0x140 [ 152.911964][ T8030] kfree+0x9e/0x3d0 [ 152.912501][ T8030] alloc_workqueue+0x7d7/0x8e0 [ 152.913182][ T8030] __btrfs_alloc_workqueue+0x11e/0x2a0 [ 152.913949][ T8030] btrfs_alloc_workqueue+0x6d/0x1d0 [ 152.914703][ T8030] scrub_workers_get+0x1e8/0x490 [ 152.915402][ T8030] btrfs_scrub_dev+0x1b9/0x9c0 [ 152.916077][ T8030] btrfs_ioctl+0x122c/0x4e50 [ 152.916729][ T8030] __x64_sys_ioctl+0x137/0x190 [ 152.917414][ T8030] do_syscall_64+0x34/0xb0 [ 152.918034][ T8030] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 152.918872][ T8030] [ 152.919203][ T8030] The buggy address belongs to the object at ffff88810d31bc00 [ 152.919203][ T8030] which belongs to the cache kmalloc-512 of size 512 [ 152.921155][ T8030] The buggy address is located 256 bytes inside of [ 152.921155][ T8030] 512-byte region [ffff88810d31bc00, ffff88810d31be00) [ 152.922993][ T8030] The buggy address belongs to the page: [ 152.923800][ T8030] page:ffffea000434c600 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10d318 [ 152.925249][ T8030] head:ffffea000434c600 order:2 compound_mapcount:0 compound_pincount:0 [ 152.926399][ T8030] flags: 0x57ff00000010200(slab|head|node=1|zone=2|lastcpupid=0x7ff) [ 152.927515][ T8030] raw: 057ff00000010200 dead000000000100 dead000000000122 ffff888009c42c80 [ 152.928716][ T8030] raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000 [ 152.929890][ T8030] page dumped because: kasan: bad access detected [ 152.930759][ T8030] [ 152.931076][ T8030] Memory state around the buggy address: [ 152.931851][ T8030] ffff88810d31bc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 152.932967][ T8030] ffff88810d31bc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 152.934068][ T8030] >ffff88810d31bd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 152.935189][ T8030] ^ [ 152.935763][ T8030] ffff88810d31bd80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 152.936847][ T8030] ffff88810d31be00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc [ 152.937940][ T8030] ================================================================== If apply_wqattrs_prepare() fails in alloc_workqueue(), it will call put_pwq() which invoke a work queue to call pwq_unbound_release_workfn() and use the 'wq'. The 'wq' allocated in alloc_workqueue() will be freed in error path when apply_wqattrs_prepare() fails. So it will lead a UAF. CPU0 CPU1 alloc_workqueue() alloc_and_link_pwqs() apply_wqattrs_prepare() fails apply_wqattrs_cleanup() schedule_work(&pwq->unbound_release_work) kfree(wq) worker_thread() pwq_unbound_release_workfn() <- trigger uaf here If apply_wqattrs_prepare() fails, the new pwq are not linked, it doesn't hold any reference to the 'wq', 'wq' is invalid to access in the worker, so add check pwq if linked to fix this. Fixes: 2d5f0764b526 ("workqueue: split apply_workqueue_attrs() into 3 stages") Cc: stable@vger.kernel.org # v4.2+ Reported-by: Hulk Robot Suggested-by: Lai Jiangshan Signed-off-by: Yang Yingliang Reviewed-by: Lai Jiangshan Tested-by: Pavel Skripkin Signed-off-by: Tejun Heo --- kernel/workqueue.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/kernel/workqueue.c b/kernel/workqueue.c index 50142fc08902..f148eacda55a 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -3676,15 +3676,21 @@ static void pwq_unbound_release_workfn(struct work_struct *work) unbound_release_work); struct workqueue_struct *wq = pwq->wq; struct worker_pool *pool = pwq->pool; - bool is_last; + bool is_last = false; - if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) - return; + /* + * when @pwq is not linked, it doesn't hold any reference to the + * @wq, and @wq is invalid to access. + */ + if (!list_empty(&pwq->pwqs_node)) { + if (WARN_ON_ONCE(!(wq->flags & WQ_UNBOUND))) + return; - mutex_lock(&wq->mutex); - list_del_rcu(&pwq->pwqs_node); - is_last = list_empty(&wq->pwqs); - mutex_unlock(&wq->mutex); + mutex_lock(&wq->mutex); + list_del_rcu(&pwq->pwqs_node); + is_last = list_empty(&wq->pwqs); + mutex_unlock(&wq->mutex); + } mutex_lock(&wq_pool_mutex); put_unbound_pool(pool); -- cgit v1.3-14-g43fede From 67f0d6d9883c13174669f88adac4f0ee656cc16a Mon Sep 17 00:00:00 2001 From: Haoran Luo Date: Wed, 21 Jul 2021 14:12:07 +0000 Subject: tracing: Fix bug in rb_per_cpu_empty() that might cause deadloop. The "rb_per_cpu_empty()" misinterpret the condition (as not-empty) when "head_page" and "commit_page" of "struct ring_buffer_per_cpu" points to the same buffer page, whose "buffer_data_page" is empty and "read" field is non-zero. An error scenario could be constructed as followed (kernel perspective): 1. All pages in the buffer has been accessed by reader(s) so that all of them will have non-zero "read" field. 2. Read and clear all buffer pages so that "rb_num_of_entries()" will return 0 rendering there's no more data to read. It is also required that the "read_page", "commit_page" and "tail_page" points to the same page, while "head_page" is the next page of them. 3. Invoke "ring_buffer_lock_reserve()" with large enough "length" so that it shot pass the end of current tail buffer page. Now the "head_page", "commit_page" and "tail_page" points to the same page. 4. Discard current event with "ring_buffer_discard_commit()", so that "head_page", "commit_page" and "tail_page" points to a page whose buffer data page is now empty. When the error scenario has been constructed, "tracing_read_pipe" will be trapped inside a deadloop: "trace_empty()" returns 0 since "rb_per_cpu_empty()" returns 0 when it hits the CPU containing such constructed ring buffer. Then "trace_find_next_entry_inc()" always return NULL since "rb_num_of_entries()" reports there's no more entry to read. Finally "trace_seq_to_user()" returns "-EBUSY" spanking "tracing_read_pipe" back to the start of the "waitagain" loop. I've also written a proof-of-concept script to construct the scenario and trigger the bug automatically, you can use it to trace and validate my reasoning above: https://github.com/aegistudio/RingBufferDetonator.git Tests has been carried out on linux kernel 5.14-rc2 (2734d6c1b1a089fb593ef6a23d4b70903526fe0c), my fixed version of kernel (for testing whether my update fixes the bug) and some older kernels (for range of affected kernels). Test result is also attached to the proof-of-concept repository. Link: https://lore.kernel.org/linux-trace-devel/YPaNxsIlb2yjSi5Y@aegistudio/ Link: https://lore.kernel.org/linux-trace-devel/YPgrN85WL9VyrZ55@aegistudio Cc: stable@vger.kernel.org Fixes: bf41a158cacba ("ring-buffer: make reentrant") Suggested-by: Linus Torvalds Signed-off-by: Haoran Luo Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ring_buffer.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index d1463eac11a3..e592d1df6f88 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -3880,10 +3880,30 @@ static bool rb_per_cpu_empty(struct ring_buffer_per_cpu *cpu_buffer) if (unlikely(!head)) return true; - return reader->read == rb_page_commit(reader) && - (commit == reader || - (commit == head && - head->read == rb_page_commit(commit))); + /* Reader should exhaust content in reader page */ + if (reader->read != rb_page_commit(reader)) + return false; + + /* + * If writers are committing on the reader page, knowing all + * committed content has been read, the ring buffer is empty. + */ + if (commit == reader) + return true; + + /* + * If writers are committing on a page other than reader page + * and head page, there should always be content to read. + */ + if (commit != head) + return false; + + /* + * Writers are committing on the head page, we just need + * to care about there're committed data, and the reader will + * swap reader page with head page when it is to read data. + */ + return rb_page_commit(commit) == 0; } /** -- cgit v1.3-14-g43fede From 3b13911a2fd0dd0146c9777a254840c5466cf120 Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Wed, 21 Jul 2021 19:10:08 -0400 Subject: tracing: Synthetic event field_pos is an index not a boolean Performing the following: ># echo 'wakeup_lat s32 pid; u64 delta; char wake_comm[]' > synthetic_events ># echo 'hist:keys=pid:__arg__1=common_timestamp.usecs' > events/sched/sched_waking/trigger ># echo 'hist:keys=next_pid:pid=next_pid,delta=common_timestamp.usecs-$__arg__1:onmatch(sched.sched_waking).trace(wakeup_lat,$pid,$delta,prev_comm)'\ > events/sched/sched_switch/trigger ># echo 1 > events/synthetic/enable Crashed the kernel: BUG: kernel NULL pointer dereference, address: 000000000000001b #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP CPU: 7 PID: 0 Comm: swapper/7 Not tainted 5.13.0-rc5-test+ #104 Hardware name: Hewlett-Packard HP Compaq Pro 6300 SFF/339A, BIOS K01 v03.03 07/14/2016 RIP: 0010:strlen+0x0/0x20 Code: f6 82 80 2b 0b bc 20 74 11 0f b6 50 01 48 83 c0 01 f6 82 80 2b 0b bc 20 75 ef c3 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 <80> 3f 00 74 10 48 89 f8 48 83 c0 01 80 38 9 f8 c3 31 RSP: 0018:ffffaa75000d79d0 EFLAGS: 00010046 RAX: 0000000000000002 RBX: ffff9cdb55575270 RCX: 0000000000000000 RDX: ffff9cdb58c7a320 RSI: ffffaa75000d7b40 RDI: 000000000000001b RBP: ffffaa75000d7b40 R08: ffff9cdb40a4f010 R09: ffffaa75000d7ab8 R10: ffff9cdb4398c700 R11: 0000000000000008 R12: ffff9cdb58c7a320 R13: ffff9cdb55575270 R14: ffff9cdb58c7a000 R15: 0000000000000018 FS: 0000000000000000(0000) GS:ffff9cdb5aa00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000001b CR3: 00000000c0612006 CR4: 00000000001706e0 Call Trace: trace_event_raw_event_synth+0x90/0x1d0 action_trace+0x5b/0x70 event_hist_trigger+0x4bd/0x4e0 ? cpumask_next_and+0x20/0x30 ? update_sd_lb_stats.constprop.0+0xf6/0x840 ? __lock_acquire.constprop.0+0x125/0x550 ? find_held_lock+0x32/0x90 ? sched_clock_cpu+0xe/0xd0 ? lock_release+0x155/0x440 ? update_load_avg+0x8c/0x6f0 ? enqueue_entity+0x18a/0x920 ? __rb_reserve_next+0xe5/0x460 ? ring_buffer_lock_reserve+0x12a/0x3f0 event_triggers_call+0x52/0xe0 trace_event_buffer_commit+0x1ae/0x240 trace_event_raw_event_sched_switch+0x114/0x170 __traceiter_sched_switch+0x39/0x50 __schedule+0x431/0xb00 schedule_idle+0x28/0x40 do_idle+0x198/0x2e0 cpu_startup_entry+0x19/0x20 secondary_startup_64_no_verify+0xc2/0xcb The reason is that the dynamic events array keeps track of the field position of the fields array, via the field_pos variable in the synth_field structure. Unfortunately, that field is a boolean for some reason, which means any field_pos greater than 1 will be a bug (in this case it was 2). Link: https://lkml.kernel.org/r/20210721191008.638bce34@oasis.local.home Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Ingo Molnar Cc: Andrew Morton Cc: stable@vger.kernel.org Fixes: bd82631d7ccdc ("tracing: Add support for dynamic strings to synthetic events") Reviewed-by: Tom Zanussi Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_synth.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/trace/trace_synth.h b/kernel/trace/trace_synth.h index 6e146b959dcd..4007fe95cf42 100644 --- a/kernel/trace/trace_synth.h +++ b/kernel/trace/trace_synth.h @@ -14,10 +14,10 @@ struct synth_field { char *name; size_t size; unsigned int offset; + unsigned int field_pos; bool is_signed; bool is_string; bool is_dynamic; - bool field_pos; }; struct synth_event { -- cgit v1.3-14-g43fede From 1e3bac71c5053c99d438771fc9fa5082ae5d90aa Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Wed, 21 Jul 2021 11:00:53 -0400 Subject: tracing/histogram: Rename "cpu" to "common_cpu" Currently the histogram logic allows the user to write "cpu" in as an event field, and it will record the CPU that the event happened on. The problem with this is that there's a lot of events that have "cpu" as a real field, and using "cpu" as the CPU it ran on, makes it impossible to run histograms on the "cpu" field of events. For example, if I want to have a histogram on the count of the workqueue_queue_work event on its cpu field, running: ># echo 'hist:keys=cpu' > events/workqueue/workqueue_queue_work/trigger Gives a misleading and wrong result. Change the command to "common_cpu" as no event should have "common_*" fields as that's a reserved name for fields used by all events. And this makes sense here as common_cpu would be a field used by all events. Now we can even do: ># echo 'hist:keys=common_cpu,cpu if cpu < 100' > events/workqueue/workqueue_queue_work/trigger ># cat events/workqueue/workqueue_queue_work/hist # event histogram # # trigger info: hist:keys=common_cpu,cpu:vals=hitcount:sort=hitcount:size=2048 if cpu < 100 [active] # { common_cpu: 0, cpu: 2 } hitcount: 1 { common_cpu: 0, cpu: 4 } hitcount: 1 { common_cpu: 7, cpu: 7 } hitcount: 1 { common_cpu: 0, cpu: 7 } hitcount: 1 { common_cpu: 0, cpu: 1 } hitcount: 1 { common_cpu: 0, cpu: 6 } hitcount: 2 { common_cpu: 0, cpu: 5 } hitcount: 2 { common_cpu: 1, cpu: 1 } hitcount: 4 { common_cpu: 6, cpu: 6 } hitcount: 4 { common_cpu: 5, cpu: 5 } hitcount: 14 { common_cpu: 4, cpu: 4 } hitcount: 26 { common_cpu: 0, cpu: 0 } hitcount: 39 { common_cpu: 2, cpu: 2 } hitcount: 184 Now for backward compatibility, I added a trick. If "cpu" is used, and the field is not found, it will fall back to "common_cpu" and work as it did before. This way, it will still work for old programs that use "cpu" to get the actual CPU, but if the event has a "cpu" as a field, it will get that event's "cpu" field, which is probably what it wants anyway. I updated the tracefs/README to include documentation about both the common_timestamp and the common_cpu. This way, if that text is present in the README, then an application can know that common_cpu is supported over just plain "cpu". Link: https://lkml.kernel.org/r/20210721110053.26b4f641@oasis.local.home Cc: Namhyung Kim Cc: Ingo Molnar Cc: Andrew Morton Cc: stable@vger.kernel.org Fixes: 8b7622bf94a44 ("tracing: Add cpu field for hist triggers") Reviewed-by: Tom Zanussi Reviewed-by: Masami Hiramatsu Signed-off-by: Steven Rostedt (VMware) --- Documentation/trace/histogram.rst | 2 +- kernel/trace/trace.c | 4 ++++ kernel/trace/trace_events_hist.c | 22 ++++++++++++++++------ 3 files changed, 21 insertions(+), 7 deletions(-) (limited to 'kernel') diff --git a/Documentation/trace/histogram.rst b/Documentation/trace/histogram.rst index b71e09f745c3..f99be8062bc8 100644 --- a/Documentation/trace/histogram.rst +++ b/Documentation/trace/histogram.rst @@ -191,7 +191,7 @@ Documentation written by Tom Zanussi with the event, in nanoseconds. May be modified by .usecs to have timestamps interpreted as microseconds. - cpu int the cpu on which the event occurred. + common_cpu int the cpu on which the event occurred. ====================== ==== ======================================= Extended error information diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index f8b80b5bab71..c59dd35a6da5 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -5609,6 +5609,10 @@ static const char readme_msg[] = "\t [:name=histname1]\n" "\t [:.]\n" "\t [if ]\n\n" + "\t Note, special fields can be used as well:\n" + "\t common_timestamp - to record current timestamp\n" + "\t common_cpu - to record the CPU the event happened on\n" + "\n" "\t When a matching event is hit, an entry is added to a hash\n" "\t table using the key(s) and value(s) named, and the value of a\n" "\t sum called 'hitcount' is incremented. Keys and values\n" diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c index 16a9dfc9fffc..34325f41ebc0 100644 --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -1111,7 +1111,7 @@ static const char *hist_field_name(struct hist_field *field, field->flags & HIST_FIELD_FL_ALIAS) field_name = hist_field_name(field->operands[0], ++level); else if (field->flags & HIST_FIELD_FL_CPU) - field_name = "cpu"; + field_name = "common_cpu"; else if (field->flags & HIST_FIELD_FL_EXPR || field->flags & HIST_FIELD_FL_VAR_REF) { if (field->system) { @@ -1991,14 +1991,24 @@ parse_field(struct hist_trigger_data *hist_data, struct trace_event_file *file, hist_data->enable_timestamps = true; if (*flags & HIST_FIELD_FL_TIMESTAMP_USECS) hist_data->attrs->ts_in_usecs = true; - } else if (strcmp(field_name, "cpu") == 0) + } else if (strcmp(field_name, "common_cpu") == 0) *flags |= HIST_FIELD_FL_CPU; else { field = trace_find_event_field(file->event_call, field_name); if (!field || !field->size) { - hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, errpos(field_name)); - field = ERR_PTR(-EINVAL); - goto out; + /* + * For backward compatibility, if field_name + * was "cpu", then we treat this the same as + * common_cpu. + */ + if (strcmp(field_name, "cpu") == 0) { + *flags |= HIST_FIELD_FL_CPU; + } else { + hist_err(tr, HIST_ERR_FIELD_NOT_FOUND, + errpos(field_name)); + field = ERR_PTR(-EINVAL); + goto out; + } } } out: @@ -5085,7 +5095,7 @@ static void hist_field_print(struct seq_file *m, struct hist_field *hist_field) seq_printf(m, "%s=", hist_field->var.name); if (hist_field->flags & HIST_FIELD_FL_CPU) - seq_puts(m, "cpu"); + seq_puts(m, "common_cpu"); else if (field_name) { if (hist_field->flags & HIST_FIELD_FL_VAR_REF || hist_field->flags & HIST_FIELD_FL_ALIAS) -- cgit v1.3-14-g43fede From 9528c19507dc9bc3d6cd96f4611d7cb80c5afcde Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Wed, 21 Jul 2021 19:53:41 -0400 Subject: tracing: Clean up alloc_synth_event() alloc_synth_event() currently has the following code to initialize the event fields and dynamic_fields: for (i = 0, j = 0; i < n_fields; i++) { event->fields[i] = fields[i]; if (fields[i]->is_dynamic) { event->dynamic_fields[j] = fields[i]; event->dynamic_fields[j]->field_pos = i; event->dynamic_fields[j++] = fields[i]; event->n_dynamic_fields++; } } 1) It would make more sense to have all fields keep track of their field_pos. 2) event->dynmaic_fields[j] is assigned twice for no reason. 3) We can move updating event->n_dynamic_fields outside the loop, and just assign it to j. This combination makes the code much cleaner. Link: https://lkml.kernel.org/r/20210721195341.29bb0f77@oasis.local.home Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_events_synth.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) (limited to 'kernel') diff --git a/kernel/trace/trace_events_synth.c b/kernel/trace/trace_events_synth.c index 2ac75eb6aa86..9315fc03e303 100644 --- a/kernel/trace/trace_events_synth.c +++ b/kernel/trace/trace_events_synth.c @@ -893,15 +893,13 @@ static struct synth_event *alloc_synth_event(const char *name, int n_fields, dyn_event_init(&event->devent, &synth_event_ops); for (i = 0, j = 0; i < n_fields; i++) { + fields[i]->field_pos = i; event->fields[i] = fields[i]; - if (fields[i]->is_dynamic) { - event->dynamic_fields[j] = fields[i]; - event->dynamic_fields[j]->field_pos = i; + if (fields[i]->is_dynamic) event->dynamic_fields[j++] = fields[i]; - event->n_dynamic_fields++; - } } + event->n_dynamic_fields = j; event->n_fields = n_fields; out: return event; -- cgit v1.3-14-g43fede From 68e83498cb4fad31963b5c76a71e80b824bc316e Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Wed, 21 Jul 2021 13:47:26 +0200 Subject: ftrace: Avoid synchronize_rcu_tasks_rude() call when not necessary synchronize_rcu_tasks_rude() triggers IPIs and forces rescheduling on all CPUs. It is a costly operation and, when targeting nohz_full CPUs, very disrupting (hence the name). So avoid calling it when 'old_hash' doesn't need to be freed. Link: https://lkml.kernel.org/r/20210721114726.1545103-1-nsaenzju@redhat.com Signed-off-by: Nicolas Saenz Julienne Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index e6fb3e6e1ffc..4fbcf560dd03 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -5985,7 +5985,8 @@ ftrace_graph_release(struct inode *inode, struct file *file) * infrastructure to do the synchronization, thus we must do it * ourselves. */ - synchronize_rcu_tasks_rude(); + if (old_hash != EMPTY_HASH) + synchronize_rcu_tasks_rude(); free_ftrace_hash(old_hash); } -- cgit v1.3-14-g43fede From 3b1a8f457fcf105924c72e99f1191834837c978d Mon Sep 17 00:00:00 2001 From: Colin Ian King Date: Wed, 21 Jul 2021 13:09:15 +0100 Subject: ftrace: Remove redundant initialization of variable ret The variable ret is being initialized with a value that is never read, it is being updated later on. The assignment is redundant and can be removed. Link: https://lkml.kernel.org/r/20210721120915.122278-1-colin.king@canonical.com Addresses-Coverity: ("Unused value") Signed-off-by: Colin Ian King Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/ftrace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index 4fbcf560dd03..7b180f61e6d3 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -7545,7 +7545,7 @@ int ftrace_is_dead(void) */ int register_ftrace_function(struct ftrace_ops *ops) { - int ret = -1; + int ret; ftrace_ops_init(ops); -- cgit v1.3-14-g43fede From 352384d5c84ebe40fa77098cc234fe173247d8ef Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (VMware)" Date: Thu, 22 Jul 2021 21:52:18 -0400 Subject: tracepoints: Update static_call before tp_funcs when adding a tracepoint Because of the significant overhead that retpolines pose on indirect calls, the tracepoint code was updated to use the new "static_calls" that can modify the running code to directly call a function instead of using an indirect caller, and this function can be changed at runtime. In the tracepoint code that calls all the registered callbacks that are attached to a tracepoint, the following is done: it_func_ptr = rcu_dereference_raw((&__tracepoint_##name)->funcs); if (it_func_ptr) { __data = (it_func_ptr)->data; static_call(tp_func_##name)(__data, args); } If there's just a single callback, the static_call is updated to just call that callback directly. Once another handler is added, then the static caller is updated to call the iterator, that simply loops over all the funcs in the array and calls each of the callbacks like the old method using indirect calling. The issue was discovered with a race between updating the funcs array and updating the static_call. The funcs array was updated first and then the static_call was updated. This is not an issue as long as the first element in the old array is the same as the first element in the new array. But that assumption is incorrect, because callbacks also have a priority field, and if there's a callback added that has a higher priority than the callback on the old array, then it will become the first callback in the new array. This means that it is possible to call the old callback with the new callback data element, which can cause a kernel panic. static_call = callback1() funcs[] = {callback1,data1}; callback2 has higher priority than callback1 CPU 1 CPU 2 ----- ----- new_funcs = {callback2,data2}, {callback1,data1} rcu_assign_pointer(tp->funcs, new_funcs); /* * Now tp->funcs has the new array * but the static_call still calls callback1 */ it_func_ptr = tp->funcs [ new_funcs ] data = it_func_ptr->data [ data2 ] static_call(callback1, data); /* Now callback1 is called with * callback2's data */ [ KERNEL PANIC ] update_static_call(iterator); To prevent this from happening, always switch the static_call to the iterator before assigning the tp->funcs to the new array. The iterator will always properly match the callback with its data. To trigger this bug: In one terminal: while :; do hackbench 50; done In another terminal echo 1 > /sys/kernel/tracing/events/sched/sched_waking/enable while :; do echo 1 > /sys/kernel/tracing/set_event_pid; sleep 0.5 echo 0 > /sys/kernel/tracing/set_event_pid; sleep 0.5 done And it doesn't take long to crash. This is because the set_event_pid adds a callback to the sched_waking tracepoint with a high priority, which will be called before the sched_waking trace event callback is called. Note, the removal to a single callback updates the array first, before changing the static_call to single callback, which is the proper order as the first element in the array is the same as what the static_call is being changed to. Link: https://lore.kernel.org/io-uring/4ebea8f0-58c9-e571-fd30-0ce4f6f09c70@samba.org/ Cc: stable@vger.kernel.org Fixes: d25e37d89dd2f ("tracepoint: Optimize using static_call()") Reported-by: Stefan Metzmacher tested-by: Stefan Metzmacher Signed-off-by: Steven Rostedt (VMware) --- kernel/tracepoint.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index 976bf8ce8039..fc32821f8240 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -299,8 +299,8 @@ static int tracepoint_add_func(struct tracepoint *tp, * a pointer to it. This array is referenced by __DO_TRACE from * include/linux/tracepoint.h using rcu_dereference_sched(). */ - rcu_assign_pointer(tp->funcs, tp_funcs); tracepoint_update_call(tp, tp_funcs, false); + rcu_assign_pointer(tp->funcs, tp_funcs); static_key_enable(&tp->key); release_probes(old); -- cgit v1.3-14-g43fede From a1833a54033e4ca760ad58fa2a6469ad59b3fa1a Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 25 Jul 2021 11:06:37 -0700 Subject: smpboot: fix duplicate and misplaced inlining directive gcc doesn't care, but clang quite reasonably pointed out that the recent commit e9ba16e68cce ("smpboot: Mark idle_init() as __always_inlined to work around aggressive compiler un-inlining") did some really odd things: kernel/smpboot.c:50:20: warning: duplicate 'inline' declaration specifier [-Wduplicate-decl-specifier] static inline void __always_inline idle_init(unsigned int cpu) ^ which not only has that duplicate inlining specifier, but the new __always_inline was put in the wrong place of the function definition. We put the storage class specifiers (ie things like "static" and "extern") first, and the type information after that. And while the compiler may not care, we put the inline specifier before the types. So it should be just static __always_inline void idle_init(unsigned int cpu) instead. Cc: Ingo Molnar Cc: Thomas Gleixner Signed-off-by: Linus Torvalds --- kernel/smpboot.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/smpboot.c b/kernel/smpboot.c index 21b7953f8242..cf6acab78538 100644 --- a/kernel/smpboot.c +++ b/kernel/smpboot.c @@ -47,7 +47,7 @@ void __init idle_thread_set_boot_cpu(void) * * Creates the thread if it does not exist. */ -static inline void __always_inline idle_init(unsigned int cpu) +static __always_inline void idle_init(unsigned int cpu) { struct task_struct *tsk = per_cpu(idle_threads, cpu); -- cgit v1.3-14-g43fede From f5e81d1117501546b7be050c5fbafa6efd2c722c Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 13 Jul 2021 08:18:31 +0000 Subject: bpf: Introduce BPF nospec instruction for mitigating Spectre v4 In case of JITs, each of the JIT backends compiles the BPF nospec instruction /either/ to a machine instruction which emits a speculation barrier /or/ to /no/ machine instruction in case the underlying architecture is not affected by Speculative Store Bypass or has different mitigations in place already. This covers both x86 and (implicitly) arm64: In case of x86, we use 'lfence' instruction for mitigation. In case of arm64, we rely on the firmware mitigation as controlled via the ssbd kernel parameter. Whenever the mitigation is enabled, it works for all of the kernel code with no need to provide any additional instructions here (hence only comment in arm64 JIT). Other archs can follow as needed. The BPF nospec instruction is specifically targeting Spectre v4 since i) we don't use a serialization barrier for the Spectre v1 case, and ii) mitigation instructions for v1 and v4 might be different on some archs. The BPF nospec is required for a future commit, where the BPF verifier does annotate intermediate BPF programs with speculation barriers. Co-developed-by: Piotr Krysiuk Co-developed-by: Benedict Schlueter Signed-off-by: Daniel Borkmann Signed-off-by: Piotr Krysiuk Signed-off-by: Benedict Schlueter Acked-by: Alexei Starovoitov --- arch/arm/net/bpf_jit_32.c | 3 +++ arch/arm64/net/bpf_jit_comp.c | 13 +++++++++++++ arch/mips/net/ebpf_jit.c | 3 +++ arch/powerpc/net/bpf_jit_comp32.c | 6 ++++++ arch/powerpc/net/bpf_jit_comp64.c | 6 ++++++ arch/riscv/net/bpf_jit_comp32.c | 4 ++++ arch/riscv/net/bpf_jit_comp64.c | 4 ++++ arch/s390/net/bpf_jit_comp.c | 5 +++++ arch/sparc/net/bpf_jit_comp_64.c | 3 +++ arch/x86/net/bpf_jit_comp.c | 7 +++++++ arch/x86/net/bpf_jit_comp32.c | 6 ++++++ include/linux/filter.h | 15 +++++++++++++++ kernel/bpf/core.c | 19 ++++++++++++++++++- kernel/bpf/disasm.c | 16 +++++++++------- 14 files changed, 102 insertions(+), 8 deletions(-) (limited to 'kernel') diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c index 897634d0a67c..a951276f0547 100644 --- a/arch/arm/net/bpf_jit_32.c +++ b/arch/arm/net/bpf_jit_32.c @@ -1602,6 +1602,9 @@ exit: rn = arm_bpf_get_reg32(src_lo, tmp2[1], ctx); emit_ldx_r(dst, rn, off, ctx, BPF_SIZE(code)); break; + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + break; /* ST: *(size *)(dst + off) = imm */ case BPF_ST | BPF_MEM | BPF_W: case BPF_ST | BPF_MEM | BPF_H: diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index dccf98a37283..41c23f474ea6 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -823,6 +823,19 @@ emit_cond_jmp: return ret; break; + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + /* + * Nothing required here. + * + * In case of arm64, we rely on the firmware mitigation of + * Speculative Store Bypass as controlled via the ssbd kernel + * parameter. Whenever the mitigation is enabled, it works + * for all of the kernel code with no need to provide any + * additional instructions. + */ + break; + /* ST: *(size *)(dst + off) = imm */ case BPF_ST | BPF_MEM | BPF_W: case BPF_ST | BPF_MEM | BPF_H: diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index 939dd06764bc..3a73e9375712 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -1355,6 +1355,9 @@ jeq_common: } break; + case BPF_ST | BPF_NOSPEC: /* speculation barrier */ + break; + case BPF_ST | BPF_B | BPF_MEM: case BPF_ST | BPF_H | BPF_MEM: case BPF_ST | BPF_W | BPF_MEM: diff --git a/arch/powerpc/net/bpf_jit_comp32.c b/arch/powerpc/net/bpf_jit_comp32.c index 34bb1583fc0c..beb12cbc8c29 100644 --- a/arch/powerpc/net/bpf_jit_comp32.c +++ b/arch/powerpc/net/bpf_jit_comp32.c @@ -737,6 +737,12 @@ int bpf_jit_build_body(struct bpf_prog *fp, u32 *image, struct codegen_context * } break; + /* + * BPF_ST NOSPEC (speculation barrier) + */ + case BPF_ST | BPF_NOSPEC: + break; + /* * BPF_ST(X) */ diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c index de8595880fee..b87a63dba9c8 100644 --- a/arch/powerpc/net/bpf_jit_comp64.c +++ b/arch/powerpc/net/bpf_jit_comp64.c @@ -627,6 +627,12 @@ emit_clear: } break; + /* + * BPF_ST NOSPEC (speculation barrier) + */ + case BPF_ST | BPF_NOSPEC: + break; + /* * BPF_ST(X) */ diff --git a/arch/riscv/net/bpf_jit_comp32.c b/arch/riscv/net/bpf_jit_comp32.c index 81de865f4c7c..e6497424cbf6 100644 --- a/arch/riscv/net/bpf_jit_comp32.c +++ b/arch/riscv/net/bpf_jit_comp32.c @@ -1251,6 +1251,10 @@ int bpf_jit_emit_insn(const struct bpf_insn *insn, struct rv_jit_context *ctx, return -1; break; + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + break; + case BPF_ST | BPF_MEM | BPF_B: case BPF_ST | BPF_MEM | BPF_H: case BPF_ST | BPF_MEM | BPF_W: diff --git a/arch/riscv/net/bpf_jit_comp64.c b/arch/riscv/net/bpf_jit_comp64.c index 87e3bf5b9086..3af4131c22c7 100644 --- a/arch/riscv/net/bpf_jit_comp64.c +++ b/arch/riscv/net/bpf_jit_comp64.c @@ -939,6 +939,10 @@ out_be: emit_ld(rd, 0, RV_REG_T1, ctx); break; + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + break; + /* ST: *(size *)(dst + off) = imm */ case BPF_ST | BPF_MEM | BPF_B: emit_imm(RV_REG_T1, imm, ctx); diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 2ae419f5115a..88419263a89a 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -1153,6 +1153,11 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp, break; } break; + /* + * BPF_NOSPEC (speculation barrier) + */ + case BPF_ST | BPF_NOSPEC: + break; /* * BPF_ST(X) */ diff --git a/arch/sparc/net/bpf_jit_comp_64.c b/arch/sparc/net/bpf_jit_comp_64.c index 4b8d3c65d266..9a2f20cbd48b 100644 --- a/arch/sparc/net/bpf_jit_comp_64.c +++ b/arch/sparc/net/bpf_jit_comp_64.c @@ -1287,6 +1287,9 @@ static int build_insn(const struct bpf_insn *insn, struct jit_ctx *ctx) return 1; break; } + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + break; /* ST: *(size *)(dst + off) = imm */ case BPF_ST | BPF_MEM | BPF_W: case BPF_ST | BPF_MEM | BPF_H: diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c index 4b951458c9fc..16d76f814e9b 100644 --- a/arch/x86/net/bpf_jit_comp.c +++ b/arch/x86/net/bpf_jit_comp.c @@ -1219,6 +1219,13 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, } break; + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + if (boot_cpu_has(X86_FEATURE_XMM2)) + /* Emit 'lfence' */ + EMIT3(0x0F, 0xAE, 0xE8); + break; + /* ST: *(u8*)(dst_reg + off) = imm */ case BPF_ST | BPF_MEM | BPF_B: if (is_ereg(dst_reg)) diff --git a/arch/x86/net/bpf_jit_comp32.c b/arch/x86/net/bpf_jit_comp32.c index 3da88ded6ee3..3bfda5f502cb 100644 --- a/arch/x86/net/bpf_jit_comp32.c +++ b/arch/x86/net/bpf_jit_comp32.c @@ -1886,6 +1886,12 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image, i++; break; } + /* speculation barrier */ + case BPF_ST | BPF_NOSPEC: + if (boot_cpu_has(X86_FEATURE_XMM2)) + /* Emit 'lfence' */ + EMIT3(0x0F, 0xAE, 0xE8); + break; /* ST: *(u8*)(dst_reg + off) = imm */ case BPF_ST | BPF_MEM | BPF_H: case BPF_ST | BPF_MEM | BPF_B: diff --git a/include/linux/filter.h b/include/linux/filter.h index 472f97074da0..83b896044e79 100644 --- a/include/linux/filter.h +++ b/include/linux/filter.h @@ -73,6 +73,11 @@ struct ctl_table_header; /* unused opcode to mark call to interpreter with arguments */ #define BPF_CALL_ARGS 0xe0 +/* unused opcode to mark speculation barrier for mitigating + * Speculative Store Bypass + */ +#define BPF_NOSPEC 0xc0 + /* As per nm, we expose JITed images as text (code) section for * kallsyms. That way, tools like perf can find it to match * addresses. @@ -390,6 +395,16 @@ static inline bool insn_is_zext(const struct bpf_insn *insn) .off = 0, \ .imm = 0 }) +/* Speculation barrier */ + +#define BPF_ST_NOSPEC() \ + ((struct bpf_insn) { \ + .code = BPF_ST | BPF_NOSPEC, \ + .dst_reg = 0, \ + .src_reg = 0, \ + .off = 0, \ + .imm = 0 }) + /* Internal classic blocks for direct assignment */ #define __BPF_STMT(CODE, K) \ diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 9b1577498373..b1a5fc04492b 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -32,6 +32,8 @@ #include #include #include + +#include #include /* Registers */ @@ -1377,6 +1379,7 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn) /* Non-UAPI available opcodes. */ [BPF_JMP | BPF_CALL_ARGS] = &&JMP_CALL_ARGS, [BPF_JMP | BPF_TAIL_CALL] = &&JMP_TAIL_CALL, + [BPF_ST | BPF_NOSPEC] = &&ST_NOSPEC, [BPF_LDX | BPF_PROBE_MEM | BPF_B] = &&LDX_PROBE_MEM_B, [BPF_LDX | BPF_PROBE_MEM | BPF_H] = &&LDX_PROBE_MEM_H, [BPF_LDX | BPF_PROBE_MEM | BPF_W] = &&LDX_PROBE_MEM_W, @@ -1621,7 +1624,21 @@ out: COND_JMP(s, JSGE, >=) COND_JMP(s, JSLE, <=) #undef COND_JMP - /* STX and ST and LDX*/ + /* ST, STX and LDX*/ + ST_NOSPEC: + /* Speculation barrier for mitigating Speculative Store Bypass. + * In case of arm64, we rely on the firmware mitigation as + * controlled via the ssbd kernel parameter. Whenever the + * mitigation is enabled, it works for all of the kernel code + * with no need to provide any additional instructions here. + * In case of x86, we use 'lfence' insn for mitigation. We + * reuse preexisting logic from Spectre v1 mitigation that + * happens to produce the required code on x86 for v4 as well. + */ +#ifdef CONFIG_X86 + barrier_nospec(); +#endif + CONT; #define LDST(SIZEOP, SIZE) \ STX_MEM_##SIZEOP: \ *(SIZE *)(unsigned long) (DST + insn->off) = SRC; \ diff --git a/kernel/bpf/disasm.c b/kernel/bpf/disasm.c index bbfc6bb79240..ca3cd9aaa6ce 100644 --- a/kernel/bpf/disasm.c +++ b/kernel/bpf/disasm.c @@ -206,15 +206,17 @@ void print_bpf_insn(const struct bpf_insn_cbs *cbs, verbose(cbs->private_data, "BUG_%02x\n", insn->code); } } else if (class == BPF_ST) { - if (BPF_MODE(insn->code) != BPF_MEM) { + if (BPF_MODE(insn->code) == BPF_MEM) { + verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n", + insn->code, + bpf_ldst_string[BPF_SIZE(insn->code) >> 3], + insn->dst_reg, + insn->off, insn->imm); + } else if (BPF_MODE(insn->code) == 0xc0 /* BPF_NOSPEC, no UAPI */) { + verbose(cbs->private_data, "(%02x) nospec\n", insn->code); + } else { verbose(cbs->private_data, "BUG_st_%02x\n", insn->code); - return; } - verbose(cbs->private_data, "(%02x) *(%s *)(r%d %+d) = %d\n", - insn->code, - bpf_ldst_string[BPF_SIZE(insn->code) >> 3], - insn->dst_reg, - insn->off, insn->imm); } else if (class == BPF_LDX) { if (BPF_MODE(insn->code) != BPF_MEM) { verbose(cbs->private_data, "BUG_ldx_%02x\n", insn->code); -- cgit v1.3-14-g43fede From 2039f26f3aca5b0e419b98f65dd36481337b86ee Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Tue, 13 Jul 2021 08:18:31 +0000 Subject: bpf: Fix leakage due to insufficient speculative store bypass mitigation Spectre v4 gadgets make use of memory disambiguation, which is a set of techniques that execute memory access instructions, that is, loads and stores, out of program order; Intel's optimization manual, section 2.4.4.5: A load instruction micro-op may depend on a preceding store. Many microarchitectures block loads until all preceding store addresses are known. The memory disambiguator predicts which loads will not depend on any previous stores. When the disambiguator predicts that a load does not have such a dependency, the load takes its data from the L1 data cache. Eventually, the prediction is verified. If an actual conflict is detected, the load and all succeeding instructions are re-executed. af86ca4e3088 ("bpf: Prevent memory disambiguation attack") tried to mitigate this attack by sanitizing the memory locations through preemptive "fast" (low latency) stores of zero prior to the actual "slow" (high latency) store of a pointer value such that upon dependency misprediction the CPU then speculatively executes the load of the pointer value and retrieves the zero value instead of the attacker controlled scalar value previously stored at that location, meaning, subsequent access in the speculative domain is then redirected to the "zero page". The sanitized preemptive store of zero prior to the actual "slow" store is done through a simple ST instruction based on r10 (frame pointer) with relative offset to the stack location that the verifier has been tracking on the original used register for STX, which does not have to be r10. Thus, there are no memory dependencies for this store, since it's only using r10 and immediate constant of zero; hence af86ca4e3088 /assumed/ a low latency operation. However, a recent attack demonstrated that this mitigation is not sufficient since the preemptive store of zero could also be turned into a "slow" store and is thus bypassed as well: [...] // r2 = oob address (e.g. scalar) // r7 = pointer to map value 31: (7b) *(u64 *)(r10 -16) = r2 // r9 will remain "fast" register, r10 will become "slow" register below 32: (bf) r9 = r10 // JIT maps BPF reg to x86 reg: // r9 -> r15 (callee saved) // r10 -> rbp // train store forward prediction to break dependency link between both r9 // and r10 by evicting them from the predictor's LRU table. 33: (61) r0 = *(u32 *)(r7 +24576) 34: (63) *(u32 *)(r7 +29696) = r0 35: (61) r0 = *(u32 *)(r7 +24580) 36: (63) *(u32 *)(r7 +29700) = r0 37: (61) r0 = *(u32 *)(r7 +24584) 38: (63) *(u32 *)(r7 +29704) = r0 39: (61) r0 = *(u32 *)(r7 +24588) 40: (63) *(u32 *)(r7 +29708) = r0 [...] 543: (61) r0 = *(u32 *)(r7 +25596) 544: (63) *(u32 *)(r7 +30716) = r0 // prepare call to bpf_ringbuf_output() helper. the latter will cause rbp // to spill to stack memory while r13/r14/r15 (all callee saved regs) remain // in hardware registers. rbp becomes slow due to push/pop latency. below is // disasm of bpf_ringbuf_output() helper for better visual context: // // ffffffff8117ee20: 41 54 push r12 // ffffffff8117ee22: 55 push rbp // ffffffff8117ee23: 53 push rbx // ffffffff8117ee24: 48 f7 c1 fc ff ff ff test rcx,0xfffffffffffffffc // ffffffff8117ee2b: 0f 85 af 00 00 00 jne ffffffff8117eee0 <-- jump taken // [...] // ffffffff8117eee0: 49 c7 c4 ea ff ff ff mov r12,0xffffffffffffffea // ffffffff8117eee7: 5b pop rbx // ffffffff8117eee8: 5d pop rbp // ffffffff8117eee9: 4c 89 e0 mov rax,r12 // ffffffff8117eeec: 41 5c pop r12 // ffffffff8117eeee: c3 ret 545: (18) r1 = map[id:4] 547: (bf) r2 = r7 548: (b7) r3 = 0 549: (b7) r4 = 4 550: (85) call bpf_ringbuf_output#194288 // instruction 551 inserted by verifier \ 551: (7a) *(u64 *)(r10 -16) = 0 | /both/ are now slow stores here // storing map value pointer r7 at fp-16 | since value of r10 is "slow". 552: (7b) *(u64 *)(r10 -16) = r7 / // following "fast" read to the same memory location, but due to dependency // misprediction it will speculatively execute before insn 551/552 completes. 553: (79) r2 = *(u64 *)(r9 -16) // in speculative domain contains attacker controlled r2. in non-speculative // domain this contains r7, and thus accesses r7 +0 below. 554: (71) r3 = *(u8 *)(r2 +0) // leak r3 As can be seen, the current speculative store bypass mitigation which the verifier inserts at line 551 is insufficient since /both/, the write of the zero sanitation as well as the map value pointer are a high latency instruction due to prior memory access via push/pop of r10 (rbp) in contrast to the low latency read in line 553 as r9 (r15) which stays in hardware registers. Thus, architecturally, fp-16 is r7, however, microarchitecturally, fp-16 can still be r2. Initial thoughts to address this issue was to track spilled pointer loads from stack and enforce their load via LDX through r10 as well so that /both/ the preemptive store of zero /as well as/ the load use the /same/ register such that a dependency is created between the store and load. However, this option is not sufficient either since it can be bypassed as well under speculation. An updated attack with pointer spill/fills now _all_ based on r10 would look as follows: [...] // r2 = oob address (e.g. scalar) // r7 = pointer to map value [...] // longer store forward prediction training sequence than before. 2062: (61) r0 = *(u32 *)(r7 +25588) 2063: (63) *(u32 *)(r7 +30708) = r0 2064: (61) r0 = *(u32 *)(r7 +25592) 2065: (63) *(u32 *)(r7 +30712) = r0 2066: (61) r0 = *(u32 *)(r7 +25596) 2067: (63) *(u32 *)(r7 +30716) = r0 // store the speculative load address (scalar) this time after the store // forward prediction training. 2068: (7b) *(u64 *)(r10 -16) = r2 // preoccupy the CPU store port by running sequence of dummy stores. 2069: (63) *(u32 *)(r7 +29696) = r0 2070: (63) *(u32 *)(r7 +29700) = r0 2071: (63) *(u32 *)(r7 +29704) = r0 2072: (63) *(u32 *)(r7 +29708) = r0 2073: (63) *(u32 *)(r7 +29712) = r0 2074: (63) *(u32 *)(r7 +29716) = r0 2075: (63) *(u32 *)(r7 +29720) = r0 2076: (63) *(u32 *)(r7 +29724) = r0 2077: (63) *(u32 *)(r7 +29728) = r0 2078: (63) *(u32 *)(r7 +29732) = r0 2079: (63) *(u32 *)(r7 +29736) = r0 2080: (63) *(u32 *)(r7 +29740) = r0 2081: (63) *(u32 *)(r7 +29744) = r0 2082: (63) *(u32 *)(r7 +29748) = r0 2083: (63) *(u32 *)(r7 +29752) = r0 2084: (63) *(u32 *)(r7 +29756) = r0 2085: (63) *(u32 *)(r7 +29760) = r0 2086: (63) *(u32 *)(r7 +29764) = r0 2087: (63) *(u32 *)(r7 +29768) = r0 2088: (63) *(u32 *)(r7 +29772) = r0 2089: (63) *(u32 *)(r7 +29776) = r0 2090: (63) *(u32 *)(r7 +29780) = r0 2091: (63) *(u32 *)(r7 +29784) = r0 2092: (63) *(u32 *)(r7 +29788) = r0 2093: (63) *(u32 *)(r7 +29792) = r0 2094: (63) *(u32 *)(r7 +29796) = r0 2095: (63) *(u32 *)(r7 +29800) = r0 2096: (63) *(u32 *)(r7 +29804) = r0 2097: (63) *(u32 *)(r7 +29808) = r0 2098: (63) *(u32 *)(r7 +29812) = r0 // overwrite scalar with dummy pointer; same as before, also including the // sanitation store with 0 from the current mitigation by the verifier. 2099: (7a) *(u64 *)(r10 -16) = 0 | /both/ are now slow stores here 2100: (7b) *(u64 *)(r10 -16) = r7 | since store unit is still busy. // load from stack intended to bypass stores. 2101: (79) r2 = *(u64 *)(r10 -16) 2102: (71) r3 = *(u8 *)(r2 +0) // leak r3 [...] Looking at the CPU microarchitecture, the scheduler might issue loads (such as seen in line 2101) before stores (line 2099,2100) because the load execution units become available while the store execution unit is still busy with the sequence of dummy stores (line 2069-2098). And so the load may use the prior stored scalar from r2 at address r10 -16 for speculation. The updated attack may work less reliable on CPU microarchitectures where loads and stores share execution resources. This concludes that the sanitizing with zero stores from af86ca4e3088 ("bpf: Prevent memory disambiguation attack") is insufficient. Moreover, the detection of stack reuse from af86ca4e3088 where previously data (STACK_MISC) has been written to a given stack slot where a pointer value is now to be stored does not have sufficient coverage as precondition for the mitigation either; for several reasons outlined as follows: 1) Stack content from prior program runs could still be preserved and is therefore not "random", best example is to split a speculative store bypass attack between tail calls, program A would prepare and store the oob address at a given stack slot and then tail call into program B which does the "slow" store of a pointer to the stack with subsequent "fast" read. From program B PoV such stack slot type is STACK_INVALID, and therefore also must be subject to mitigation. 2) The STACK_SPILL must not be coupled to register_is_const(&stack->spilled_ptr) condition, for example, the previous content of that memory location could also be a pointer to map or map value. Without the fix, a speculative store bypass is not mitigated in such precondition and can then lead to a type confusion in the speculative domain leaking kernel memory near these pointer types. While brainstorming on various alternative mitigation possibilities, we also stumbled upon a retrospective from Chrome developers [0]: [...] For variant 4, we implemented a mitigation to zero the unused memory of the heap prior to allocation, which cost about 1% when done concurrently and 4% for scavenging. Variant 4 defeats everything we could think of. We explored more mitigations for variant 4 but the threat proved to be more pervasive and dangerous than we anticipated. For example, stack slots used by the register allocator in the optimizing compiler could be subject to type confusion, leading to pointer crafting. Mitigating type confusion for stack slots alone would have required a complete redesign of the backend of the optimizing compiler, perhaps man years of work, without a guarantee of completeness. [...] From BPF side, the problem space is reduced, however, options are rather limited. One idea that has been explored was to xor-obfuscate pointer spills to the BPF stack: [...] // preoccupy the CPU store port by running sequence of dummy stores. [...] 2106: (63) *(u32 *)(r7 +29796) = r0 2107: (63) *(u32 *)(r7 +29800) = r0 2108: (63) *(u32 *)(r7 +29804) = r0 2109: (63) *(u32 *)(r7 +29808) = r0 2110: (63) *(u32 *)(r7 +29812) = r0 // overwrite scalar with dummy pointer; xored with random 'secret' value // of 943576462 before store ... 2111: (b4) w11 = 943576462 2112: (af) r11 ^= r7 2113: (7b) *(u64 *)(r10 -16) = r11 2114: (79) r11 = *(u64 *)(r10 -16) 2115: (b4) w2 = 943576462 2116: (af) r2 ^= r11 // ... and restored with the same 'secret' value with the help of AX reg. 2117: (71) r3 = *(u8 *)(r2 +0) [...] While the above would not prevent speculation, it would make data leakage infeasible by directing it to random locations. In order to be effective and prevent type confusion under speculation, such random secret would have to be regenerated for each store. The additional complexity involved for a tracking mechanism that prevents jumps such that restoring spilled pointers would not get corrupted is not worth the gain for unprivileged. Hence, the fix in here eventually opted for emitting a non-public BPF_ST | BPF_NOSPEC instruction which the x86 JIT translates into a lfence opcode. Inserting the latter in between the store and load instruction is one of the mitigations options [1]. The x86 instruction manual notes: [...] An LFENCE that follows an instruction that stores to memory might complete before the data being stored have become globally visible. [...] The latter meaning that the preceding store instruction finished execution and the store is at minimum guaranteed to be in the CPU's store queue, but it's not guaranteed to be in that CPU's L1 cache at that point (globally visible). The latter would only be guaranteed via sfence. So the load which is guaranteed to execute after the lfence for that local CPU would have to rely on store-to-load forwarding. [2], in section 2.3 on store buffers says: [...] For every store operation that is added to the ROB, an entry is allocated in the store buffer. This entry requires both the virtual and physical address of the target. Only if there is no free entry in the store buffer, the frontend stalls until there is an empty slot available in the store buffer again. Otherwise, the CPU can immediately continue adding subsequent instructions to the ROB and execute them out of order. On Intel CPUs, the store buffer has up to 56 entries. [...] One small upside on the fix is that it lifts constraints from af86ca4e3088 where the sanitize_stack_off relative to r10 must be the same when coming from different paths. The BPF_ST | BPF_NOSPEC gets emitted after a BPF_STX or BPF_ST instruction. This happens either when we store a pointer or data value to the BPF stack for the first time, or upon later pointer spills. The former needs to be enforced since otherwise stale stack data could be leaked under speculation as outlined earlier. For non-x86 JITs the BPF_ST | BPF_NOSPEC mapping is currently optimized away, but others could emit a speculation barrier as well if necessary. For real-world unprivileged programs e.g. generated by LLVM, pointer spill/fill is only generated upon register pressure and LLVM only tries to do that for pointers which are not used often. The program main impact will be the initial BPF_ST | BPF_NOSPEC sanitation for the STACK_INVALID case when the first write to a stack slot occurs e.g. upon map lookup. In future we might refine ways to mitigate the latter cost. [0] https://arxiv.org/pdf/1902.05178.pdf [1] https://msrc-blog.microsoft.com/2018/05/21/analysis-and-mitigation-of-speculative-store-bypass-cve-2018-3639/ [2] https://arxiv.org/pdf/1905.05725.pdf Fixes: af86ca4e3088 ("bpf: Prevent memory disambiguation attack") Fixes: f7cf25b2026d ("bpf: track spill/fill of constants") Co-developed-by: Piotr Krysiuk Co-developed-by: Benedict Schlueter Signed-off-by: Daniel Borkmann Signed-off-by: Piotr Krysiuk Signed-off-by: Benedict Schlueter Acked-by: Alexei Starovoitov --- include/linux/bpf_verifier.h | 2 +- kernel/bpf/verifier.c | 87 ++++++++++++++++---------------------------- 2 files changed, 33 insertions(+), 56 deletions(-) (limited to 'kernel') diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index 7ba7e800d472..828d08afeee0 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -340,8 +340,8 @@ struct bpf_insn_aux_data { }; u64 map_key_state; /* constant (32 bit) key tracking for maps */ int ctx_field_size; /* the ctx field size for load insn, maybe 0 */ - int sanitize_stack_off; /* stack slot to be cleared */ u32 seen; /* this insn was processed by the verifier at env->pass_cnt */ + bool sanitize_stack_spill; /* subject to Spectre v4 sanitation */ bool zext_dst; /* this insn zero extends dst reg */ u8 alu_state; /* used in combination with alu_limit */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 657062cb4d85..f9bda5476ea5 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -2610,6 +2610,19 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, cur = env->cur_state->frame[env->cur_state->curframe]; if (value_regno >= 0) reg = &cur->regs[value_regno]; + if (!env->bypass_spec_v4) { + bool sanitize = reg && is_spillable_regtype(reg->type); + + for (i = 0; i < size; i++) { + if (state->stack[spi].slot_type[i] == STACK_INVALID) { + sanitize = true; + break; + } + } + + if (sanitize) + env->insn_aux_data[insn_idx].sanitize_stack_spill = true; + } if (reg && size == BPF_REG_SIZE && register_is_bounded(reg) && !register_is_null(reg) && env->bpf_capable) { @@ -2632,47 +2645,10 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env, verbose(env, "invalid size of register spill\n"); return -EACCES; } - if (state != cur && reg->type == PTR_TO_STACK) { verbose(env, "cannot spill pointers to stack into stack frame of the caller\n"); return -EINVAL; } - - if (!env->bypass_spec_v4) { - bool sanitize = false; - - if (state->stack[spi].slot_type[0] == STACK_SPILL && - register_is_const(&state->stack[spi].spilled_ptr)) - sanitize = true; - for (i = 0; i < BPF_REG_SIZE; i++) - if (state->stack[spi].slot_type[i] == STACK_MISC) { - sanitize = true; - break; - } - if (sanitize) { - int *poff = &env->insn_aux_data[insn_idx].sanitize_stack_off; - int soff = (-spi - 1) * BPF_REG_SIZE; - - /* detected reuse of integer stack slot with a pointer - * which means either llvm is reusing stack slot or - * an attacker is trying to exploit CVE-2018-3639 - * (speculative store bypass) - * Have to sanitize that slot with preemptive - * store of zero. - */ - if (*poff && *poff != soff) { - /* disallow programs where single insn stores - * into two different stack slots, since verifier - * cannot sanitize them - */ - verbose(env, - "insn %d cannot access two stack slots fp%d and fp%d", - insn_idx, *poff, soff); - return -EINVAL; - } - *poff = soff; - } - } save_register_state(state, spi, reg); } else { u8 type = STACK_MISC; @@ -11913,35 +11889,33 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) for (i = 0; i < insn_cnt; i++, insn++) { bpf_convert_ctx_access_t convert_ctx_access; + bool ctx_access; if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) || insn->code == (BPF_LDX | BPF_MEM | BPF_H) || insn->code == (BPF_LDX | BPF_MEM | BPF_W) || - insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) + insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) { type = BPF_READ; - else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || - insn->code == (BPF_STX | BPF_MEM | BPF_H) || - insn->code == (BPF_STX | BPF_MEM | BPF_W) || - insn->code == (BPF_STX | BPF_MEM | BPF_DW)) + ctx_access = true; + } else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) || + insn->code == (BPF_STX | BPF_MEM | BPF_H) || + insn->code == (BPF_STX | BPF_MEM | BPF_W) || + insn->code == (BPF_STX | BPF_MEM | BPF_DW) || + insn->code == (BPF_ST | BPF_MEM | BPF_B) || + insn->code == (BPF_ST | BPF_MEM | BPF_H) || + insn->code == (BPF_ST | BPF_MEM | BPF_W) || + insn->code == (BPF_ST | BPF_MEM | BPF_DW)) { type = BPF_WRITE; - else + ctx_access = BPF_CLASS(insn->code) == BPF_STX; + } else { continue; + } if (type == BPF_WRITE && - env->insn_aux_data[i + delta].sanitize_stack_off) { + env->insn_aux_data[i + delta].sanitize_stack_spill) { struct bpf_insn patch[] = { - /* Sanitize suspicious stack slot with zero. - * There are no memory dependencies for this store, - * since it's only using frame pointer and immediate - * constant of zero - */ - BPF_ST_MEM(BPF_DW, BPF_REG_FP, - env->insn_aux_data[i + delta].sanitize_stack_off, - 0), - /* the original STX instruction will immediately - * overwrite the same stack slot with appropriate value - */ *insn, + BPF_ST_NOSPEC(), }; cnt = ARRAY_SIZE(patch); @@ -11955,6 +11929,9 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env) continue; } + if (!ctx_access) + continue; + switch (env->insn_aux_data[i + delta].ptr_type) { case PTR_TO_CTX: if (!ops->convert_ctx_access) -- cgit v1.3-14-g43fede