From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753849AbaEHLsJ (ORCPT ); Thu, 8 May 2014 07:48:09 -0400 Received: from mail.efficios.com ([78.47.125.74]:45346 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753317AbaEHLsF (ORCPT ); Thu, 8 May 2014 07:48:05 -0400 From: Mathieu Desnoyers To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , Sasha Levin , Oleg Nesterov , Dave Jones Subject: [PATCH] Fix: tracepoint: use after rcu free Date: Thu, 8 May 2014 07:47:49 -0400 Message-Id: <1399549669-25465-1-git-send-email-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org commit de7b2973903c6cc50b31ee5682a69b2219b9919d Author: Mathieu Desnoyers Date: Tue Apr 8 17:26:21 2014 -0400 tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints introduces a use after free by calling release_probes on the old struct tracepoint array before the newly allocated array is published with rcu_assign_pointer. There is a race window where tracepoints (RCU readers) can perform a "use-after-grace-period-after-free", which shows up as a GPF in stress-tests. Link: https://lkml.org/lkml/2014/5/6/738 Signed-off-by: Mathieu Desnoyers CC: Steven Rostedt CC: Sasha Levin CC: Oleg Nesterov CC: Dave Jones --- kernel/tracepoint.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c index ac5b23c..6620e58 100644 --- a/kernel/tracepoint.c +++ b/kernel/tracepoint.c @@ -188,7 +188,6 @@ static int tracepoint_add_func(struct tracepoint *tp, WARN_ON_ONCE(1); return PTR_ERR(old); } - release_probes(old); /* * rcu_assign_pointer has a smp_wmb() which makes sure that the new @@ -200,6 +199,7 @@ static int tracepoint_add_func(struct tracepoint *tp, rcu_assign_pointer(tp->funcs, tp_funcs); if (!static_key_enabled(&tp->key)) static_key_slow_inc(&tp->key); + release_probes(old); return 0; } @@ -221,7 +221,6 @@ static int tracepoint_remove_func(struct tracepoint *tp, WARN_ON_ONCE(1); return PTR_ERR(old); } - release_probes(old); if (!tp_funcs) { /* Removed last function */ @@ -232,6 +231,7 @@ static int tracepoint_remove_func(struct tracepoint *tp, static_key_slow_dec(&tp->key); } rcu_assign_pointer(tp->funcs, tp_funcs); + release_probes(old); return 0; } -- 1.7.10.4