From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754082Ab2KVTUQ (ORCPT ); Thu, 22 Nov 2012 14:20:16 -0500 Received: from na3sys010aog103.obsmtp.com ([74.125.245.74]:48371 "HELO na3sys010aog103.obsmtp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S965176Ab2KVTUJ (ORCPT ); Thu, 22 Nov 2012 14:20:09 -0500 From: Roland Dreier To: Jens Axboe Cc: linux-kernel@vger.kernel.org Subject: [PATCH] block: Don't access request after it might be freed Date: Thu, 22 Nov 2012 02:00:11 -0800 Message-Id: <1353578411-23527-1-git-send-email-roland@kernel.org> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Roland Dreier After we've done __elv_add_request() and __blk_run_queue() in blk_execute_rq_nowait(), the request might finish and be freed immediately. Therefore checking if the type is REQ_TYPE_PM_RESUME isn't safe afterwards, because if it isn't, rq might be gone. Instead, check beforehand and stash the result in a temporary. This fixes crashes in blk_execute_rq_nowait() I get occasionally when running with lots of memory debugging options enabled -- I think this race is usually harmless because the window for rq to be reallocated is so small. Signed-off-by: Roland Dreier --- block/blk-exec.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/block/blk-exec.c b/block/blk-exec.c index 8b6dc5b..f71eac3 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -52,11 +52,17 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, rq_end_io_fn *done) { int where = at_head ? ELEVATOR_INSERT_FRONT : ELEVATOR_INSERT_BACK; + bool is_pm_resume; WARN_ON(irqs_disabled()); rq->rq_disk = bd_disk; rq->end_io = done; + /* + * need to check this before __blk_run_queue(), because rq can + * be freed before that returns. + */ + is_pm_resume = rq->cmd_type == REQ_TYPE_PM_RESUME; spin_lock_irq(q->queue_lock); @@ -71,7 +77,7 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk, __elv_add_request(q, rq, where); __blk_run_queue(q); /* the queue is stopped so it won't be run */ - if (rq->cmd_type == REQ_TYPE_PM_RESUME) + if (is_pm_resume) q->request_fn(q); spin_unlock_irq(q->queue_lock); } -- 1.7.10.4