Messages in this thread Patch in this message | | | Date | Wed, 27 May 2015 03:01:07 -0700 | From | tip-bot for Alexei Starovoitov <> | Subject | [tip:perf/core] perf: Fix race in BPF program unregister |
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Commit-ID: dead9f29ddcc69551f35529a252d2704047870d3 Gitweb: http://git.kernel.org/tip/dead9f29ddcc69551f35529a252d2704047870d3 Author: Alexei Starovoitov <ast@plumgrid.com> AuthorDate: Fri, 15 May 2015 12:15:21 -0700 Committer: Ingo Molnar <mingo@kernel.org> 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 <wangnan0@huawei.com> Signed-off-by: Alexei Starovoitov <ast@plumgrid.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Arnaldo Carvalho de Melo <acme@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: lizefan@huawei.com Cc: pi3orama@163.com Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes") Link: http://lkml.kernel.org/r/1431717321-28772-1-git-send-email-ast@plumgrid.com Signed-off-by: Ingo Molnar <mingo@kernel.org> --- 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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