Messages in this thread | | | Date | Wed, 20 May 2015 08:58:23 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH tip] perf/events/core: fix race in bpf program unregister |
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On Tue, May 19, 2015 at 10:27:05PM -0700, Alexei Starovoitov wrote: > 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.
Thanks, queued for perf/urgent.
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