[PATCH] mmc: block: fixed NULL pointer dereference

[PATCH] mmc: block: fixed NULL pointer dereference

[Jaehoon Chung]

Hi.

I send to mailing for [RFC] Kernel NULL pointer dereference.
This patch is fixed it.

In similar case, when discard request, check condition and
performed mmc_blk_issue_rw_rq(mq, NULL) for ongoing async transfer.

But When flush request, entered the mmc_blk_issue_flush() then return.
(then didn't complete ongoing aync transfer).

I think that need to complete for ongoing aync transfer before flush request.

I tested with this patch, it's working fine.
(SDHCI controller, eMMC4.41)

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
---
 drivers/mmc/card/block.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
index 38d0149..1ff5486 100644
--- a/drivers/mmc/card/block.c
+++ b/drivers/mmc/card/block.c
@@ -1200,6 +1200,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
 		else
 			ret = mmc_blk_issue_discard_rq(mq, req);
 	} else if (req && req->cmd_flags & REQ_FLUSH) {
+		/* complete ongoing async transfer before issuing flush */
+		if (card->host->areq)
+			mmc_blk_issue_rw_rq(mq, NULL);
 		ret = mmc_blk_issue_flush(mq, req);
 	} else {
 		ret = mmc_blk_issue_rw_rq(mq, req);

Re: [PATCH] mmc: block: fixed NULL pointer dereference

[Per Forlin]

On 13 July 2011 10:02, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> Hi.
>
> I send to mailing for [RFC] Kernel NULL pointer dereference.
> This patch is fixed it.
>
> In similar case, when discard request, check condition and
> performed mmc_blk_issue_rw_rq(mq, NULL) for ongoing async transfer.
>
> But When flush request, entered the mmc_blk_issue_flush() then return.
> (then didn't complete ongoing aync transfer).
>
> I think that need to complete for ongoing aync transfer before flush request.
>
I did consider this when I added the check for discard but I didn't
realize it is necessary for flush too.
There is no real downside of completing the async request before flush
in terms of performance anyway.

Thanks for catching this bug.

> @@ -1200,6 +1200,9 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
>                else
>                        ret = mmc_blk_issue_discard_rq(mq, req);
>        } else if (req && req->cmd_flags & REQ_FLUSH) {
> +               /* complete ongoing async transfer before issuing flush */
> +               if (card->host->areq)
> +                       mmc_blk_issue_rw_rq(mq, NULL);
These 2 lines are the same as for the discard condition. I still
prefer 2 lines of repeating code rather than one big if-statement
covering both discard and flush.

Acked-by: Per Forlin <per.forlin@linaro.org>

Regards,
Per