2013-10-24 22:13:42

by Ray Jui

Subject: [PATCH] mmc: fix host release issue after discard operation

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;
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

2013-10-25 10:42:52

by Seungwon Jeon

Subject: RE: [PATCH] mmc: fix host release issue after discard operation

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

2013-10-26 00:40:45

by Ray Jui

Subject: Re: [PATCH] mmc: fix host release issue after discard operation

On 10/25/2013 3:42 AM, Seungwon Jeon wrote:
> 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
>
>
Hi Seungwon,

I like your suggestion. It makes the code simpler. I'll make the change
and submit patch v2.

Thanks,

Ray Jui