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Date: Fri, 7 Mar 2014 17:08:01 -0800 From: Greg Kroah-Hartman <gregkh@...uxfoundation.org> To: linux-kernel@...r.kernel.org Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, stable@...r.kernel.org, Roland Dreier <roland@...estorage.com>, Jens Axboe <axboe@...nel.dk>, Rui Xiang <rui.xiang@...wei.com> Subject: [PATCH 3.4 65/99] block: Dont access request after it might be freed 3.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Roland Dreier <roland@...estorage.com> 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@...estorage.com> Signed-off-by: Jens Axboe <axboe@...nel.dk> [xr: Backported to 3.4: adjust context] Signed-off-by: Rui Xiang <rui.xiang@...wei.com> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org> --- block/blk-exec.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/block/blk-exec.c +++ b/block/blk-exec.c @@ -49,8 +49,18 @@ void blk_execute_rq_nowait(struct reques 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); if (unlikely(blk_queue_dead(q))) { @@ -66,7 +76,7 @@ void blk_execute_rq_nowait(struct reques __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); } -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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