[PATCH] null_blk: fix use-after-free error

[PATCH] null_blk: fix use-after-free error

[Mike Krinkin]

blk_end_request_all may free request, so we need to save
request_queue pointer before blk_end_request_all call.

The problem was introduced in commit cf8ecc5a8455266f8d51
("null_blk: guarantee device restart in all irq modes")
and causes general protection fault with slab poisoning
enabled.

Fixes: cf8ecc5a8455266f8d51 ("null_blk: guarantee device
       restart in all irq modes")

Signed-off-by: Mike Krinkin <krinkin.m.u@gmail.com>
---
 drivers/block/null_blk.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
index 36c4651..6a06e3e 100644
--- a/drivers/block/null_blk.c
+++ b/drivers/block/null_blk.c
@@ -219,6 +219,9 @@ static void end_cmd(struct nullb_cmd *cmd)
 {
 	struct request_queue *q = NULL;
 
+	if (cmd->rq)
+		q = cmd->rq->q;
+
 	switch (queue_mode)  {
 	case NULL_Q_MQ:
 		blk_mq_end_request(cmd->rq, 0);
@@ -232,9 +235,6 @@ static void end_cmd(struct nullb_cmd *cmd)
 		goto free_cmd;
 	}
 
-	if (cmd->rq)
-		q = cmd->rq->q;
-
 	/* Restart queue if needed, as we are freeing a tag */
 	if (q && !q->mq_ops && blk_queue_stopped(q)) {
 		unsigned long flags;
-- 
1.9.1

Re: [PATCH] null_blk: fix use-after-free error

[Ming Lei]

On Tue, Dec 15, 2015 at 5:56 PM, Mike Krinkin <krinkin.m.u@gmail.com> wrote:
> blk_end_request_all may free request, so we need to save
> request_queue pointer before blk_end_request_all call.
>
> The problem was introduced in commit cf8ecc5a8455266f8d51
> ("null_blk: guarantee device restart in all irq modes")
> and causes general protection fault with slab poisoning
> enabled.
>
> Fixes: cf8ecc5a8455266f8d51 ("null_blk: guarantee device
>        restart in all irq modes")
>
> Signed-off-by: Mike Krinkin <krinkin.m.u@gmail.com>

Reviewed-by: Ming Lei <tom.leiming@gmail.com>

> ---
>  drivers/block/null_blk.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/block/null_blk.c b/drivers/block/null_blk.c
> index 36c4651..6a06e3e 100644
> --- a/drivers/block/null_blk.c
> +++ b/drivers/block/null_blk.c
> @@ -219,6 +219,9 @@ static void end_cmd(struct nullb_cmd *cmd)
>  {
>         struct request_queue *q = NULL;
>
> +       if (cmd->rq)
> +               q = cmd->rq->q;
> +
>         switch (queue_mode)  {
>         case NULL_Q_MQ:
>                 blk_mq_end_request(cmd->rq, 0);
> @@ -232,9 +235,6 @@ static void end_cmd(struct nullb_cmd *cmd)
>                 goto free_cmd;
>         }
>
> -       if (cmd->rq)
> -               q = cmd->rq->q;
> -
>         /* Restart queue if needed, as we are freeing a tag */
>         if (q && !q->mq_ops && blk_queue_stopped(q)) {
>                 unsigned long flags;
> --
> 1.9.1
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at  http://www.tux.org/lkml/



-- 
Ming Lei

Re: [PATCH] null_blk: fix use-after-free error

[Jens Axboe]

On 12/15/2015 02:56 AM, Mike Krinkin wrote:
> blk_end_request_all may free request, so we need to save
> request_queue pointer before blk_end_request_all call.
>
> The problem was introduced in commit cf8ecc5a8455266f8d51
> ("null_blk: guarantee device restart in all irq modes")
> and causes general protection fault with slab poisoning
> enabled.
>
> Fixes: cf8ecc5a8455266f8d51 ("null_blk: guarantee device
>         restart in all irq modes")

Added for 4.4, thanks.

-- 
Jens Axboe