From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933648Ab3GZVar (ORCPT ); Fri, 26 Jul 2013 17:30:47 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:50872 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759952Ab3GZUsv (ORCPT ); Fri, 26 Jul 2013 16:48:51 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Kent Overstreet Subject: [ 48/79] bcache: Fix a dumb race Date: Fri, 26 Jul 2013 13:47:38 -0700 Message-Id: <20130726204727.540501940@linuxfoundation.org> X-Mailer: git-send-email 1.8.3.rc0.20.gb99dd2e In-Reply-To: <20130726204721.849052763@linuxfoundation.org> References: <20130726204721.849052763@linuxfoundation.org> User-Agent: quilt/0.60-5.1.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Kent Overstreet commit 6aa8f1a6ca41c49721d2de4e048d3da8d06411f9 upstream. In the far-too-complicated closure code - closures can have destructors, for probably dubious reasons; they get run after the closure is no longer waiting on anything but before dropping the parent ref, intended just for freeing whatever memory the closure is embedded in. Trouble is, when remaining goes to 0 and we've got nothing more to run - we also have to unlock the closure, setting remaining to -1. If there's a destructor, that unlock isn't doing anything - nobody could be trying to lock it if we're about to free it - but if the unlock _is needed... that check for a destructor was racy. Argh. Signed-off-by: Kent Overstreet Signed-off-by: Greg Kroah-Hartman --- drivers/md/bcache/closure.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) --- a/drivers/md/bcache/closure.c +++ b/drivers/md/bcache/closure.c @@ -66,16 +66,18 @@ static inline void closure_put_after_sub } else { struct closure *parent = cl->parent; struct closure_waitlist *wait = closure_waitlist(cl); + closure_fn *destructor = cl->fn; closure_debug_destroy(cl); + smp_mb(); atomic_set(&cl->remaining, -1); if (wait) closure_wake_up(wait); - if (cl->fn) - cl->fn(cl); + if (destructor) + destructor(cl); if (parent) closure_put(parent);