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authorRoland Dreier <roland@purestorage.com>2012-11-22 02:00:11 -0800
committerBen Hutchings <ben@decadent.org.uk>2012-12-06 11:20:35 +0000
commit32eb44e290d1151e9eb26f57564dae6966190685 (patch)
treeadd2e86801ceab4d9fd8fd543e240c0ec7e98a71
parentde268a9f92b3b2504e9f87db3b4dd609aafb255f (diff)
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 <roland@purestorage.com> Signed-off-by: Jens Axboe <axboe@kernel.dk> [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
-rw-r--r--block/blk-exec.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/block/blk-exec.c b/block/blk-exec.c
index 60532852b3ab..ac2c6e7f0538 100644
--- a/block/blk-exec.c
+++ b/block/blk-exec.c
@@ -49,6 +49,7 @@ 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;
if (unlikely(blk_queue_dead(q))) {
rq->errors = -ENXIO;
@@ -59,12 +60,18 @@ void blk_execute_rq_nowait(struct request_queue *q, struct gendisk *bd_disk,
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;
+
WARN_ON(irqs_disabled());
spin_lock_irq(q->queue_lock);
__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);
}