From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753910AbaEHNFX (ORCPT ); Thu, 8 May 2014 09:05:23 -0400 Received: from cdptpa-outbound-snat.email.rr.com ([107.14.166.230]:32018 "EHLO cdptpa-oedge-vip.email.rr.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752756AbaEHNFW (ORCPT ); Thu, 8 May 2014 09:05:22 -0400 Date: Thu, 8 May 2014 09:05:20 -0400 From: Steven Rostedt To: Mathieu Desnoyers Cc: linux-kernel@vger.kernel.org, Sasha Levin , Oleg Nesterov , Dave Jones Subject: Re: [PATCH] Fix: tracepoint: use after rcu free Message-ID: <20140508090520.2b225a94@gandalf.local.home> In-Reply-To: <1399549669-25465-1-git-send-email-mathieu.desnoyers@efficios.com> References: <1399549669-25465-1-git-send-email-mathieu.desnoyers@efficios.com> X-Mailer: Claws Mail 3.9.3 (GTK+ 2.24.22; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-RR-Connecting-IP: 107.14.168.118:25 X-Cloudmark-Score: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 ... > 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. We can also include a (even though it's redundant) Fixes: de7b2973903c "tracepoint: Use struct pointer instead of name hash for reg/unreg tracepoints" I'll update the change log to reflect my comments and then pull this into my urgent branch and start testing it. 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; > } >