Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755506AbbBUDw6 (ORCPT ); Fri, 20 Feb 2015 22:52:58 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33052 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755440AbbBUDw4 (ORCPT ); Fri, 20 Feb 2015 22:52:56 -0500 Date: Fri, 20 Feb 2015 21:52:50 -0600 From: Josh Poimboeuf To: Jiri Kosina Cc: Petr Mladek , sjenning@redhat.com, vojtech@suse.cz, masami.hiramatsu.pt@hitachi.com, mbenes@suse.cz, live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] livepatch: RCU protect struct klp_func all the time when used in klp_ftrace_handler() Message-ID: <20150221035250.GA15563@treble.redhat.com> References: <1424278933-26952-1-git-send-email-pmladek@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1479 Lines: 43 On Sat, Feb 21, 2015 at 12:29:30AM +0100, Jiri Kosina wrote: > On Wed, 18 Feb 2015, Petr Mladek wrote: > > > func->new_func has been accessed after rcu_read_unlock() in klp_ftrace_handler() > > and therefore the access was not protected. > > > > Signed-off-by: Petr Mladek > > --- > > kernel/livepatch/core.c | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c > > index ff7f47d026ac..cde66192e20e 100644 > > --- a/kernel/livepatch/core.c > > +++ b/kernel/livepatch/core.c > > @@ -314,12 +314,12 @@ static void notrace klp_ftrace_handler(unsigned long ip, > > rcu_read_lock(); > > func = list_first_or_null_rcu(&ops->func_stack, struct klp_func, > > stack_node); > > - rcu_read_unlock(); > > - > > if (WARN_ON_ONCE(!func)) > > - return; > > + goto unlock; > > > > klp_arch_set_pc(regs, (unsigned long)func->new_func); > > +unlock: > > + rcu_read_unlock(); > > This can't hurt, even though the only scenario where this could in theory > trigger as a bug (module removal) is non-issue now. > > But I'd like to take it nevertheless ... Seth, Josh? Acked-by: Josh Poimboeuf -- Josh -- 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/