Commit-ID: dead9f29ddcc69551f35529a252d2704047870d3
Gitweb: http://git.kernel.org/tip/dead9f29ddcc69551f35529a252d2704047870d3
Author: Alexei Starovoitov <[email protected]>
AuthorDate: Fri, 15 May 2015 12:15:21 -0700
Committer: Ingo Molnar <[email protected]>
CommitDate: Wed, 27 May 2015 08:46:15 +0200
perf: Fix race in BPF program unregister
there is a race between perf_event_free_bpf_prog() and free_trace_kprobe():
__free_event()
event->destroy(event)
tp_perf_event_destroy()
perf_trace_destroy()
perf_trace_event_unreg()
which is dropping event->tp_event->perf_refcount and allows to proceed in:
unregister_trace_kprobe()
unregister_kprobe_event()
trace_remove_event_call()
probe_remove_event_call()
free_trace_kprobe()
while __free_event does:
call_rcu(&event->rcu_head, free_event_rcu);
free_event_rcu()
perf_event_free_bpf_prog()
To fix the race simply move perf_event_free_bpf_prog() before
event->destroy(), since event->tp_event is still valid at that point.
Note, perf_trace_destroy() is not racing with trace_remove_event_call()
since they both grab event_mutex.
Reported-by: Wang Nan <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Cc: [email protected]
Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to
kprobes")
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>
---
kernel/events/core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1a3bf48..eddf1ed 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3442,7 +3442,6 @@ static void free_event_rcu(struct rcu_head *head)
if (event->ns)
put_pid_ns(event->ns);
perf_event_free_filter(event);
- perf_event_free_bpf_prog(event);
kfree(event);
}
@@ -3573,6 +3572,8 @@ static void __free_event(struct perf_event *event)
put_callchain_buffers();
}
+ perf_event_free_bpf_prog(event);
+
if (event->destroy)
event->destroy(event);
--
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