From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754143AbaEHNI0 (ORCPT ); Thu, 8 May 2014 09:08:26 -0400 Received: from mail.efficios.com ([78.47.125.74]:45618 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751169AbaEHNIZ (ORCPT ); Thu, 8 May 2014 09:08:25 -0400 Date: Thu, 8 May 2014 13:08:25 +0000 (UTC) From: Mathieu Desnoyers To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Sasha Levin , Oleg Nesterov , Dave Jones Message-ID: <55466295.13096.1399554505453.JavaMail.zimbra@efficios.com> In-Reply-To: <20140508090520.2b225a94@gandalf.local.home> References: <1399549669-25465-1-git-send-email-mathieu.desnoyers@efficios.com> <20140508090520.2b225a94@gandalf.local.home> Subject: Re: [PATCH] Fix: tracepoint: use after rcu free MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Originating-IP: [206.248.138.119] X-Mailer: Zimbra 8.0.5_GA_5839 (ZimbraWebClient - FF29 (Linux)/8.0.5_GA_5839) Thread-Topic: tracepoint: use after rcu free Thread-Index: 67mE9L/USgNFrDujZsUB0d92vC9KVA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ----- Original Message ----- > From: "Steven Rostedt" > To: "Mathieu Desnoyers" > Cc: linux-kernel@vger.kernel.org, "Sasha Levin" , "Oleg Nesterov" , "Dave > Jones" > Sent: Thursday, May 8, 2014 9:05:20 AM > Subject: Re: [PATCH] Fix: tracepoint: use after rcu free > > On Thu, 8 May 2014 07:47:49 -0400 > Mathieu Desnoyers wrote: > > > commit de7b2973903c6cc50b31ee5682a69b2219b9919d > > Author: Mathieu Desnoyers > > Date: Tue Apr 8 17:26:21 2014 -0400 > > Hi Mathieu, > > Thanks for the quick fix. > > > > > > 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 > > Note when talking about commits already in mainline, use the first 12 > characters of the commit sha1 followed by the subject. Like so: > > Commit de7b2973903c "tracepoint: Use struct pointer instead of name > hash for reg/unreg tracepoints" introduces a use after free ... OK, will do. > > > > 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 > > Also, Link tags need to point to lkml.kernel.org. > > Link: http://lkml.kernel.org/r/53698021.5020108@oracle.com > > Which is "lkml.kernel.org/r/" followed by the Message-ID. OK > > We can also include a (even though it's redundant) > > Fixes: de7b2973903c "tracepoint: Use struct pointer instead of name hash for > reg/unreg tracepoints" Thanks for the pointers, I'll keep those in mind for my next patches. > > I'll update the change log to reflect my comments and then pull this > into my urgent branch and start testing it. Thanks! Mathieu > > Thanks, > > -- Steve > > > 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; > > } > > > > -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com