2015-12-15 09:56:50

by Mike Krinkin

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

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 <[email protected]>
---
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

2015-12-22 02:11:30

by Ming Lei

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

On Tue, Dec 15, 2015 at 5:56 PM, Mike Krinkin <[email protected]> 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 <[email protected]>

Reviewed-by: Ming Lei <[email protected]>

> ---
> 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
>
> --
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--
Ming Lei

2015-12-22 17:43:21

by Jens Axboe

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

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