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ublk: fix NULL pointer dereference in ublk_ctrl_set_size() 

ublk_ctrl_set_size() unconditionally dereferences ub->ub_disk via
set_capacity_and_notify() without checking if it is NULL.

ub->ub_disk is NULL before UBLK_CMD_START_DEV completes (it is only
assigned in ublk_ctrl_start_dev()) and after UBLK_CMD_STOP_DEV runs
(ublk_detach_disk() sets it to NULL). Since the UBLK_CMD_UPDATE_SIZE
handler performs no state validation, a user can trigger a NULL pointer
dereference by sending UPDATE_SIZE to a device that has been added but
not yet started, or one that has been stopped.

Fix this by checking ub->ub_disk under ub->mutex before dereferencing
it, and returning -ENODEV if the disk is not available.

Fixes: 98b995660b ("ublk: Add UBLK_U_CMD_UPDATE_SIZE")
Cc: stable@vger.kernel.org
Signed-off-by: Mehul Rao <mehulrao@gmail.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Mehul Rao 2026-03-05 14:31:46 -05:00 committed by Jens Axboe
parent ce8ee8583e
commit 25966fc097
1 changed files with 9 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

12
drivers/block/ublk_drv.c
View File

@ -5003,15 +5003,22 @@ static int ublk_ctrl_get_features(const struct ublksrv_ctrl_cmd *header)
return 0;
}
static void ublk_ctrl_set_size(struct ublk_device *ub, const struct ublksrv_ctrl_cmd *header)
static int ublk_ctrl_set_size(struct ublk_device *ub, const struct ublksrv_ctrl_cmd *header)
{
struct ublk_param_basic *p = &ub->params.basic;
u64 new_size = header->data[0];
int ret = 0;
mutex_lock(&ub->mutex);
if (!ub->ub_disk) {
ret = -ENODEV;
goto out;
}
p->dev_sectors = new_size;
set_capacity_and_notify(ub->ub_disk, p->dev_sectors);
out:
mutex_unlock(&ub->mutex);
return ret;
}
struct count_busy {
@ -5331,8 +5338,7 @@ static int ublk_ctrl_uring_cmd(struct io_uring_cmd *cmd,
ret = ublk_ctrl_end_recovery(ub, &header);
break;
case UBLK_CMD_UPDATE_SIZE:
ublk_ctrl_set_size(ub, &header);
ret = 0;
ret = ublk_ctrl_set_size(ub, &header);
break;
case UBLK_CMD_QUIESCE_DEV:
ret = ublk_ctrl_quiesce_dev(ub, &header);