From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752066AbbE0LBz (ORCPT ); Wed, 27 May 2015 07:01:55 -0400 Received: from terminus.zytor.com ([198.137.202.10]:34096 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751364AbbE0LBw (ORCPT ); Wed, 27 May 2015 07:01:52 -0400 Date: Wed, 27 May 2015 03:01:07 -0700 From: tip-bot for Alexei Starovoitov Message-ID: Cc: acme@infradead.org, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org, hpa@zytor.com, tglx@linutronix.de, peterz@infradead.org, ast@plumgrid.com, wangnan0@huawei.com, mingo@kernel.org Reply-To: mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de, wangnan0@huawei.com, ast@plumgrid.com, hpa@zytor.com, linux-kernel@vger.kernel.org, torvalds@linux-foundation.org, acme@infradead.org In-Reply-To: <1431717321-28772-1-git-send-email-ast@plumgrid.com> References: <1431717321-28772-1-git-send-email-ast@plumgrid.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf: Fix race in BPF program unregister Git-Commit-ID: dead9f29ddcc69551f35529a252d2704047870d3 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: dead9f29ddcc69551f35529a252d2704047870d3 Gitweb: http://git.kernel.org/tip/dead9f29ddcc69551f35529a252d2704047870d3 Author: Alexei Starovoitov AuthorDate: Fri, 15 May 2015 12:15:21 -0700 Committer: Ingo Molnar 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 Signed-off-by: Alexei Starovoitov Signed-off-by: Peter Zijlstra (Intel) Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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 --- 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);