From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754405Ab1HAXat (ORCPT ); Mon, 1 Aug 2011 19:30:49 -0400 Received: from cantor2.suse.de ([195.135.220.15]:38893 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754149Ab1HAX1a (ORCPT ); Mon, 1 Aug 2011 19:27:30 -0400 X-Mailbox-Line: From gregkh@clark.kroah.org Mon Aug 1 16:20:54 2011 Message-Id: <20110801232054.099166038@clark.kroah.org> User-Agent: quilt/0.48-16.4 Date: Mon, 01 Aug 2011 16:18:50 -0700 From: Greg KH To: linux-kernel@vger.kernel.org, stable@kernel.org Cc: stable-review@kernel.org, torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Trond Myklebust Subject: [35/70] SUNRPC: Fix a race between work-queue and rpc_killall_tasks In-Reply-To: <20110801232124.GA15313@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 2.6.39-stable review patch. If anyone has any objections, please let us know. ------------------ From: Trond Myklebust commit b55c59892e1f3b6c7d4b9ccffb4263e1486fb990 upstream. Since rpc_killall_tasks may modify the rpc_task's tk_action field without any locking, we need to be careful when dereferencing it. Reported-by: Ben Greear Tested-by: Ben Greear Signed-off-by: Trond Myklebust Signed-off-by: Greg Kroah-Hartman --- net/sunrpc/sched.c | 27 +++++++++++---------------- 1 file changed, 11 insertions(+), 16 deletions(-) --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -616,30 +616,25 @@ static void __rpc_execute(struct rpc_tas BUG_ON(RPC_IS_QUEUED(task)); for (;;) { + void (*do_action)(struct rpc_task *); /* - * Execute any pending callback. + * Execute any pending callback first. */ - if (task->tk_callback) { - void (*save_callback)(struct rpc_task *); - - /* - * We set tk_callback to NULL before calling it, - * in case it sets the tk_callback field itself: - */ - save_callback = task->tk_callback; - task->tk_callback = NULL; - save_callback(task); - } else { + do_action = task->tk_callback; + task->tk_callback = NULL; + if (do_action == NULL) { /* * Perform the next FSM step. - * tk_action may be NULL when the task has been killed - * by someone else. + * tk_action may be NULL if the task has been killed. + * In particular, note that rpc_killall_tasks may + * do this at any time, so beware when dereferencing. */ - if (task->tk_action == NULL) + do_action = task->tk_action; + if (do_action == NULL) break; - task->tk_action(task); } + do_action(task); /* * Lockless check for whether task is sleeping or not.