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

[Liu Xiaodong]

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@xxxxxxxxx>
---
 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