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authorYonghong Song <yhs@fb.com>2017-10-30 13:50:22 -0700
committerDavid S. Miller <davem@davemloft.net>2017-11-01 12:35:48 +0900
commit07c41a295c5f25928a7cb689fdec816bd0089fe8 (patch)
tree069bf405b725d169ce806019e0d4a612d31b456c /kernel/trace/bpf_trace.c
parentnet: sit: Update lookup to handle links set to L3 slave (diff)
downloadlinux-dev-07c41a295c5f25928a7cb689fdec816bd0089fe8.tar.xz
linux-dev-07c41a295c5f25928a7cb689fdec816bd0089fe8.zip
bpf: avoid rcu_dereference inside bpf_event_mutex lock region
During perf event attaching/detaching bpf programs, the tp_event->prog_array change is protected by the bpf_event_mutex lock in both attaching and deteching functions. Although tp_event->prog_array is a rcu pointer, rcu_derefrence is not needed to access it since mutex lock will guarantee ordering. Verified through "make C=2" that sparse locking check still happy with the new change. Also change the label name in perf_event_{attach,detach}_bpf_prog from "out" to "unlock" to reflect the code action after the label. Signed-off-by: Yonghong Song <yhs@fb.com> Acked-by: Alexei Starovoitov <ast@kernel.org> Acked-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to '')
-rw-r--r--kernel/trace/bpf_trace.c17
1 files changed, 7 insertions, 10 deletions
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 136aa6bb0422..506efe6e8ed9 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -769,20 +769,19 @@ int perf_event_attach_bpf_prog(struct perf_event *event,
mutex_lock(&bpf_event_mutex);
if (event->prog)
- goto out;
+ goto unlock;
- old_array = rcu_dereference_protected(event->tp_event->prog_array,
- lockdep_is_held(&bpf_event_mutex));
+ old_array = event->tp_event->prog_array;
ret = bpf_prog_array_copy(old_array, NULL, prog, &new_array);
if (ret < 0)
- goto out;
+ goto unlock;
/* set the new array to event->tp_event and set event->prog */
event->prog = prog;
rcu_assign_pointer(event->tp_event->prog_array, new_array);
bpf_prog_array_free(old_array);
-out:
+unlock:
mutex_unlock(&bpf_event_mutex);
return ret;
}
@@ -796,11 +795,9 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
mutex_lock(&bpf_event_mutex);
if (!event->prog)
- goto out;
-
- old_array = rcu_dereference_protected(event->tp_event->prog_array,
- lockdep_is_held(&bpf_event_mutex));
+ goto unlock;
+ old_array = event->tp_event->prog_array;
ret = bpf_prog_array_copy(old_array, event->prog, NULL, &new_array);
if (ret < 0) {
bpf_prog_array_delete_safe(old_array, event->prog);
@@ -812,6 +809,6 @@ void perf_event_detach_bpf_prog(struct perf_event *event)
bpf_prog_put(event->prog);
event->prog = NULL;
-out:
+unlock:
mutex_unlock(&bpf_event_mutex);
}