Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755521Ab0GJOmv (ORCPT ); Sat, 10 Jul 2010 10:42:51 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:46927 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753333Ab0GJOmu (ORCPT ); Sat, 10 Jul 2010 10:42:50 -0400 Message-ID: <4C3886E5.8060506@us.ibm.com> Date: Sat, 10 Jul 2010 07:42:45 -0700 From: Darren Hart User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.10) Gecko/20100528 Thunderbird/3.0.5 MIME-Version: 1.0 To: rostedt@goodmis.org CC: linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Eric Dumazet , John Kacur , Mike Galbraith , linux-rt-users@vger.kernel.org Subject: Re: [PATCH 1/4] rtmutex: avoid null derefence in WARN_ON References: <1278714780-788-1-git-send-email-dvhltc@us.ibm.com> <1278714780-788-2-git-send-email-dvhltc@us.ibm.com> <1278721788.1537.170.camel@gandalf.stny.rr.com> In-Reply-To: <1278721788.1537.170.camel@gandalf.stny.rr.com> Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1896 Lines: 63 On 07/09/2010 05:29 PM, Steven Rostedt wrote: > On Fri, 2010-07-09 at 15:32 -0700, Darren Hart wrote: >> If the pi_blocked_on variable is NULL, the subsequent WARN_ON's >> will cause an OOPS. Only perform the susequent checks if >> pi_blocked_on is valid. >> >> Signed-off-by: Darren Hart >> Cc: Thomas Gleixner >> Cc: Peter Zijlstra >> Cc: Ingo Molnar >> Cc: Eric Dumazet >> Cc: John Kacur >> Cc: Steven Rostedt >> Cc: Mike Galbraith >> --- >> kernel/rtmutex.c | 7 ++++--- >> 1 files changed, 4 insertions(+), 3 deletions(-) >> >> diff --git a/kernel/rtmutex.c b/kernel/rtmutex.c >> index 23dd443..baac7d9 100644 >> --- a/kernel/rtmutex.c >> +++ b/kernel/rtmutex.c >> @@ -579,9 +579,10 @@ static void wakeup_next_waiter(struct rt_mutex *lock, int savestate) >> >> raw_spin_lock(&pendowner->pi_lock); >> >> - WARN_ON(!pendowner->pi_blocked_on); >> - WARN_ON(pendowner->pi_blocked_on != waiter); >> - WARN_ON(pendowner->pi_blocked_on->lock != lock); >> + if (!WARN_ON(!pendowner->pi_blocked_on)) { >> + WARN_ON(pendowner->pi_blocked_on != waiter); > > The above actually has no issue if the pi_blocked_on is NULL. It doesn't, but it's also redundant and makes the console noisier for no reason. Seemed worth while to drop it under the if in the same go. -- Darren > The below, well yeah. > > -- Steve > >> + WARN_ON(pendowner->pi_blocked_on->lock != lock); >> + } >> >> pendowner->pi_blocked_on = NULL; >> > > -- Darren Hart IBM Linux Technology Center Real-Time Linux Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/