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| author |   Paul E. McKenney <paulmck@kernel.org> | 2020-09-15 14:27:38 -0700 |
|---|---|---|
| committer | Paul E. McKenney <paulmck@kernel.org> | 2020-09-16 16:32:38 -0700 |
| commit | f747c7e15d7bc71a967a94ceda686cf2460b69e8 (patch) | |
| tree | 07b0f92d5e84dccbaf622e5765be228188cc13f2 /kernel/rcu | |
| parent | rcu-tasks: Fix low-probability task_struct leak (diff) | |
| download | linux-dev-f747c7e15d7bc71a967a94ceda686cf2460b69e8.tar.xz linux-dev-f747c7e15d7bc71a967a94ceda686cf2460b69e8.zip | |
rcu-tasks: Enclose task-list scan in rcu_read_lock()
The rcu_tasks_trace_postgp() function uses for_each_process_thread()
to scan the task list without the benefit of RCU read-side protection,
which can result in use-after-free errors on task_struct structures.
This error was missed because the TRACE01 rcutorture scenario enables
lockdep, but also builds with CONFIG_PREEMPT_NONE=y. In this situation,
preemption is disabled everywhere, so lockdep thinks everywhere can
be a legitimate RCU reader. This commit therefore adds the needed
rcu_read_lock() and rcu_read_unlock().
Note that this bug can occur only after an RCU Tasks Trace CPU stall
warning, which by default only happens after a grace period has extended
for ten minutes (yes, not a typo, minutes).
Fixes: 4593e772b502 ("rcu-tasks: Add stall warnings for RCU Tasks Trace")
Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: <bpf@vger.kernel.org>
Cc: <stable@vger.kernel.org> # 5.7.x
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Diffstat (limited to 'kernel/rcu')
| -rw-r--r-- | kernel/rcu/tasks.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index fcd9c25f1140..d5d9f2d03e8a 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1088,9 +1088,11 @@ static void rcu_tasks_trace_postgp(struct rcu_tasks *rtp) if (ret) break; // Count reached zero. // Stall warning time, so make a list of the offenders. + rcu_read_lock(); for_each_process_thread(g, t) if (READ_ONCE(t->trc_reader_special.b.need_qs)) trc_add_holdout(t, &holdouts); + rcu_read_unlock(); firstreport = true; list_for_each_entry_safe(t, g, &holdouts, trc_holdout_list) { if (READ_ONCE(t->trc_reader_special.b.need_qs)) |