Messages in this thread | | | Date | Tue, 19 May 2015 22:27:05 -0700 | From | Alexei Starovoitov <> | Subject | Re: [PATCH tip] perf/events/core: fix race in bpf program unregister |
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On 5/15/15 12:15 PM, Alexei Starovoitov wrote: > 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. > > Fixes: 2541517c32be ("tracing, perf: Implement BPF programs attached to kprobes") > Reported-by: Wang Nan <wangnan0@huawei.com> > Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
ping. This is needed in 4.1.
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