2023-01-31 07:06:09

by Liu Xiaodong

Subject: [PATCH] block: ublk: extending queue_size to fix overflow

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 <[email protected]>
---
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

2023-01-31 10:16:18

by Ming Lei

Subject: Re: [PATCH] block: ublk: extending queue_size to fix overflow

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 <[email protected]>
> ---
> 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 <[email protected]>


Thanks,
Ming

2023-01-31 15:00:50

by Jens Axboe

Subject: Re: [PATCH] block: ublk: extending queue_size to fix overflow

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