When validating drafted SPDK ublk target, in a case that
assigning large queue depth to multiqueue ublk device,
ublk target would run into a weird incorrect state. During
rounds of review and debug, An overflow bug was found
in ublk driver.

In ublk_cmd.h, UBLK_MAX_QUEUE_DEPTH is 4096 which means
each ublk queue depth can be set as large as 4096. But
when setting qd for a ublk device,
sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io)
will be larger than 65535 if qd is larger than 2728.
Then queue_size is overflowed, and ublk_get_queue()
references a wrong pointer position. The wrong content of
ublk_queue elements will lead to out-of-bounds memory
access.

Extend queue_size in ublk_device as "unsigned int".

Signed-off-by: Liu Xiaodong <xiaodong.liu@intel.com>
---
 drivers/block/ublk_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
index e54693204630..6368b56eacf1 100644
--- a/drivers/block/ublk_drv.c
+++ b/drivers/block/ublk_drv.c
@@ -137,7 +137,7 @@ struct ublk_device {
 
 	char	*__queues;
 
-	unsigned short  queue_size;
+	unsigned int	queue_size;
 	struct ublksrv_ctrl_dev_info	dev_info;
 
 	struct blk_mq_tag_set	tag_set;
-- 
2.14.5

On Tue, 31 Jan 2023 02:05:52 -0500, Liu Xiaodong wrote:
> When validating drafted SPDK ublk target, in a case that
> assigning large queue depth to multiqueue ublk device,
> ublk target would run into a weird incorrect state. During
> rounds of review and debug, An overflow bug was found
> in ublk driver.
> 
> In ublk_cmd.h, UBLK_MAX_QUEUE_DEPTH is 4096 which means
> each ublk queue depth can be set as large as 4096. But
> when setting qd for a ublk device,
> sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io)
> will be larger than 65535 if qd is larger than 2728.
> Then queue_size is overflowed, and ublk_get_queue()
> references a wrong pointer position. The wrong content of
> ublk_queue elements will lead to out-of-bounds memory
> access.
> 
> [...]

Applied, thanks!

[1/1] block: ublk: extending queue_size to fix overflow
      commit: 29baef789c838bd5c02f50c88adbbc6b955aaf61

Best regards,
-- 
Jens Axboe

On Tue, Jan 31, 2023 at 02:05:52AM -0500, Liu Xiaodong wrote:
> When validating drafted SPDK ublk target, in a case that
> assigning large queue depth to multiqueue ublk device,
> ublk target would run into a weird incorrect state. During
> rounds of review and debug, An overflow bug was found
> in ublk driver.
> 
> In ublk_cmd.h, UBLK_MAX_QUEUE_DEPTH is 4096 which means
> each ublk queue depth can be set as large as 4096. But
> when setting qd for a ublk device,
> sizeof(struct ublk_queue) + depth * sizeof(struct ublk_io)
> will be larger than 65535 if qd is larger than 2728.
> Then queue_size is overflowed, and ublk_get_queue()
> references a wrong pointer position. The wrong content of
> ublk_queue elements will lead to out-of-bounds memory
> access.
> 
> Extend queue_size in ublk_device as "unsigned int".
> 
> Signed-off-by: Liu Xiaodong <xiaodong.liu@intel.com>
> ---
>  drivers/block/ublk_drv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index e54693204630..6368b56eacf1 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -137,7 +137,7 @@ struct ublk_device {
>  
>  	char	*__queues;
>  
> -	unsigned short  queue_size;
> +	unsigned int	queue_size;
>  	struct ublksrv_ctrl_dev_info	dev_info;

Good catch,

Fixes: 71f28f3136af ("ublk_drv: add io_uring based userspace block driver")

Reviewed-by: Ming Lei <ming.lei@redhat.com>


Thanks,
Ming