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Subject[PATCH 1/2] mmc: v4.14: Fix null pointer dereference in mmc_init_request
Date
It is possible for queuedata to be cleared in mmc_cleanup_queue before
the request has been started. This will result in dereferencing a null
pointer.

Signed-off-by: Raul E Rangel <rrangel@chromium.org>
---
I think we should cherry-pick 41e3efd07d5a02c80f503e29d755aa1bbb4245de
https://lore.kernel.org/patchwork/patch/856512/ into 4.14. It fixes a
potential resource leak when shutting down the request queue. Once this
patch is applied, there is a potential for a null pointer dereference.
That's what this patch fixes. The next patch is just an optimization to
stop processing earlier.

See https://patchwork.kernel.org/patch/10925469/ for the initial
motivation.

This commit applies to v4.14.116.

This doesn't apply to 5.1 since mmc has been migrated to blk-mq.

Thanks,
Raul

drivers/mmc/core/queue.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/mmc/core/queue.c b/drivers/mmc/core/queue.c
index 0a4e77a5ba33..4bf1a9c6440b 100644
--- a/drivers/mmc/core/queue.c
+++ b/drivers/mmc/core/queue.c
@@ -159,8 +159,14 @@ static int mmc_init_request(struct request_queue *q, struct request *req,
{
struct mmc_queue_req *mq_rq = req_to_mmc_queue_req(req);
struct mmc_queue *mq = q->queuedata;
- struct mmc_card *card = mq->card;
- struct mmc_host *host = card->host;
+ struct mmc_card *card;
+ struct mmc_host *host;
+
+ if (!mq)
+ return -ENODEV;
+
+ card = mq->card;
+ host = card->host;

mq_rq->sg = mmc_alloc_sg(host->max_segs, gfp);
if (!mq_rq->sg)
--
2.21.0.1020.gf2820cf01a-goog
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