Hi Ray,
On Fri, October 25, 2013, Ray Jui wrote:
> Under function mmc_blk_issue_rq, after an MMC discard operation,
> the MMC request data structure may be freed in memory. Later in
> the same function, the check of req->cmd_flags & MMC_REQ_SPECIAL_MASK
> is dangerous and invalid. It causes the MMC host not being released
> when it should
>
> This patch fixes the issue by marking the special request down before
> the discard/flush operation
>
> Reported by: Harold (SoonYeal) Yang <[email protected]>
> Signed-off-by: Ray Jui <[email protected]>
> ---
> drivers/mmc/card/block.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/mmc/card/block.c b/drivers/mmc/card/block.c
> index 1a3163f..9e8e970 100644
> --- a/drivers/mmc/card/block.c
> +++ b/drivers/mmc/card/block.c
> @@ -1954,7 +1954,7 @@ static int mmc_blk_issue_rw_rq(struct mmc_queue *mq,
> struct request *rqc)
>
> static int mmc_blk_issue_rq(struct mmc_queue *mq, struct request *req)
> {
> - int ret;
> + int ret, req_is_special = 0;
It would be better to use boolean?
Either, in a different way, I considered to save the cmd_flags like below.
unsigned int cmd_flags = req ? req->cmd_flags : 0;
Then, we could replace several 'if statement' without dereference.
if (req && req->cmd_flags & REQ_DISCARD) -> if (cmd_flags & REQ_DISCARD)
Just my suggestion.
Thanks,
Seungwon Jeon
> struct mmc_blk_data *md = mq->data;
> struct mmc_card *card = md->queue.card;
> struct mmc_host *host = card->host;
> @@ -1973,6 +1973,10 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq,
> struct request *req)
> goto out;
> }
>
> + /* mark special request here since req may be freed later */
> + if (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK))
> + req_is_special = 1;
> +
> mq->flags &= ~MMC_QUEUE_NEW_REQUEST;
> if (req && req->cmd_flags & REQ_DISCARD) {
> /* complete ongoing async transfer before issuing discard */
> @@ -1999,7 +2003,7 @@ static int mmc_blk_issue_rq(struct mmc_queue *mq,
> struct request *req)
>
> out:
> if ((!req && !(mq->flags & MMC_QUEUE_NEW_REQUEST)) ||
> - (req && (req->cmd_flags & MMC_REQ_SPECIAL_MASK)))
> + req_is_special)
> /*
> * Release host when there are no more requests
> * and after special request(discard, flush) is done.
> --
> 1.7.9.5
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