From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932773Ab2LMOiC (ORCPT ); Thu, 13 Dec 2012 09:38:02 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:44647 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932678Ab2LMOJW (ORCPT ); Thu, 13 Dec 2012 09:09:22 -0500 From: Herton Ronaldo Krzesinski To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Cc: Roland Dreier , Jens Axboe , Herton Ronaldo Krzesinski Subject: [PATCH 139/241] block: Don't access request after it might be freed Date: Thu, 13 Dec 2012 11:58:24 -0200 Message-Id: <1355407206-17100-140-git-send-email-herton.krzesinski@canonical.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1355407206-17100-1-git-send-email-herton.krzesinski@canonical.com> References: <1355407206-17100-1-git-send-email-herton.krzesinski@canonical.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.5.7.2 -stable review patch. If anyone has any objections, please let me know. ------------------ From: Roland Dreier commit 893d290f1d7496db97c9471bc352ad4a11dc8a25 upstream. 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 Signed-off-by: Jens Axboe [ herton: adjust context ] Signed-off-by: Herton Ronaldo Krzesinski --- block/blk-exec.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/block/blk-exec.c b/block/blk-exec.c index fb2cbd5..9925fbe 100644 --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -49,8 +49,16 @@ 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()); + + /* + * 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); if (unlikely(blk_queue_dead(q))) { @@ -66,7 +74,7 @@ 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); } -- 1.7.9.5