[PATCH 4.19 32/72] dm ioctl: fix out of bounds array access when no devices

From: Greg Kroah-Hartman
Date: Mon Mar 29 2021 - 04:14:01 EST


From: Mikulas Patocka <mpatocka@xxxxxxxxxx>

commit 4edbe1d7bcffcd6269f3b5eb63f710393ff2ec7a upstream.

If there are not any dm devices, we need to zero the "dev" argument in
the first structure dm_name_list. However, this can cause out of
bounds write, because the "needed" variable is zero and len may be
less than eight.

Fix this bug by reporting DM_BUFFER_FULL_FLAG if the result buffer is
too small to hold the "nl->dev" value.

Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Reported-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/dm-ioctl.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -529,7 +529,7 @@ static int list_devices(struct file *fil
* Grab our output buffer.
*/
nl = orig_nl = get_result_buffer(param, param_size, &len);
- if (len < needed) {
+ if (len < needed || len < sizeof(nl->dev)) {
param->flags |= DM_BUFFER_FULL_FLAG;
goto out;
}