[PATCH stable] dm ioctl: fix out of bounds array access when no devices

[PATCH stable] dm ioctl: fix out of bounds array access when no devices

[Ard Biesheuvel]

From: Mikulas Patocka <mpatocka@redhat.com>

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@redhat.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
Please apply to 4.4.y and 4.9.y

 drivers/md/dm-ioctl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 836a2808c0c7..eb2659a12310 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -524,7 +524,7 @@ static int list_devices(struct dm_ioctl *param, size_t param_size)
 	 * Grab our output buffer.
 	 */
 	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;
 	}
-- 
2.20.1

Re: [PATCH stable] dm ioctl: fix out of bounds array access when no devices

[Sasha Levin]

On Wed, May 19, 2021 at 09:41:24AM +0200, Ard Biesheuvel wrote:
>From: Mikulas Patocka <mpatocka@redhat.com>
>
>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@redhat.com>
>Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
>Cc: stable@vger.kernel.org
>Signed-off-by: Mike Snitzer <snitzer@redhat.com>
>Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>---
>Please apply to 4.4.y and 4.9.y

We already carry this patch via the backport provided in
https://lore.kernel.org/stable/20210513094552.266451-1-nobuhiro1.iwamatsu@toshiba.co.jp/


-- 
Thanks,
Sasha

Re: [PATCH stable] dm ioctl: fix out of bounds array access when no devices

[Ard Biesheuvel]

On Wed, 19 May 2021 at 16:56, Sasha Levin <sashal@kernel.org> wrote:
>
> On Wed, May 19, 2021 at 09:41:24AM +0200, Ard Biesheuvel wrote:
> >From: Mikulas Patocka <mpatocka@redhat.com>
> >
> >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@redhat.com>
> >Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> >Cc: stable@vger.kernel.org
> >Signed-off-by: Mike Snitzer <snitzer@redhat.com>
> >Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> >---
> >Please apply to 4.4.y and 4.9.y
>
> We already carry this patch via the backport provided in
> https://lore.kernel.org/stable/20210513094552.266451-1-nobuhiro1.iwamatsu@toshiba.co.jp/
>

Excellent, thanks.