From patchwork Mon Dec 10 14:20:11 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [3.5.y.z, extended, stable] Patch "block: Don't access request after it might be freed" has been added to staging queue Date: Mon, 10 Dec 2012 04:20:11 -0000 From: Herton Ronaldo Krzesinski X-Patchwork-Id: 204921 Message-Id: <1355149211-9542-1-git-send-email-herton.krzesinski@canonical.com> To: Roland Dreier Cc: Jens Axboe , kernel-team@lists.ubuntu.com This is a note to let you know that I have just added a patch titled block: Don't access request after it might be freed to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.5.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Herton ------ >From ee5cf30456f95be755b0e6502132c535903aa89f Mon Sep 17 00:00:00 2001 From: Roland Dreier Date: Thu, 22 Nov 2012 02:00:11 -0800 Subject: [PATCH] block: Don't access request after it might be freed 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(-) -- 1.7.9.5 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); }