From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754937AbbEOTPb (ORCPT ); Fri, 15 May 2015 15:15:31 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:36668 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752912AbbEOTP2 (ORCPT ); Fri, 15 May 2015 15:15:28 -0400 From: Alexei Starovoitov To: Ingo Molnar Cc: Peter Zijlstra , Arnaldo Carvalho de Melo , Wang Nan , lizefan@huawei.com, pi3orama@163.com, linux-kernel@vger.kernel.org Subject: [PATCH tip] perf/events/core: fix race in bpf program unregister Date: Fri, 15 May 2015 12:15:21 -0700 Message-Id: <1431717321-28772-1-git-send-email-ast@plumgrid.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 Signed-off-by: Alexei Starovoitov --- Wang, please test the fix to double check. 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 84231a146dd5..b27bdc8b3558 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3415,7 +3415,6 @@ 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); } @@ -3546,6 +3545,8 @@ static void __free_event(struct perf_event *event) put_callchain_buffers(); } + perf_event_free_bpf_prog(event); + if (event->destroy) event->destroy(event); -- 1.7.9.5