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authorAlexei Starovoitov <[email protected]>2015-05-15 12:15:21 -0700
committerIngo Molnar <[email protected]>2015-05-27 08:46:15 +0200
commitdead9f29ddcc69551f35529a252d2704047870d3 (patch)
tree2f89c58475dd28534155aae9175cd94299bf58e7
parentba155e2d21f6bf05de86a78dbe5bfd8757604a65 (diff)
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]>
-rw-r--r--kernel/events/core.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1a3bf48743ce..eddf1ed4155e 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);