Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755459AbbBTX3d (ORCPT ); Fri, 20 Feb 2015 18:29:33 -0500 Received: from cantor2.suse.de ([195.135.220.15]:38578 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755171AbbBTX3c (ORCPT ); Fri, 20 Feb 2015 18:29:32 -0500 Date: Sat, 21 Feb 2015 00:29:30 +0100 (CET) From: Jiri Kosina To: Petr Mladek cc: jpoimboe@redhat.com, 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() In-Reply-To: <1424278933-26952-1-git-send-email-pmladek@suse.cz> Message-ID: References: <1424278933-26952-1-git-send-email-pmladek@suse.cz> User-Agent: Alpine 2.00 (LNX 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1332 Lines: 43 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? Thanks, -- Jiri Kosina SUSE Labs -- 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/