[PATCH 3.11 183/198] ALSA: control: Make sure that id->index does not overflow

[Luis Henriques]

3.11.10.13 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lars-Peter Clausen <lars at metafoo.de>

commit 883a1d49f0d77d30012f114b2e19fc141beb3e8e upstream.

The ALSA control code expects that the range of assigned indices to a control is
continuous and does not overflow. Currently there are no checks to enforce this.
If a control with a overflowing index range is created that control becomes
effectively inaccessible and unremovable since snd_ctl_find_id() will not be
able to find it. This patch adds a check that makes sure that controls with a
overflowing index range can not be created.

Signed-off-by: Lars-Peter Clausen <lars at metafoo.de>
Acked-by: Jaroslav Kysela <perex at perex.cz>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 sound/core/control.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sound/core/control.c b/sound/core/control.c
index 93215b4bec6b..98a29b26c5f4 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -343,6 +343,9 @@ int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)
 	if (snd_BUG_ON(!card || !kcontrol->info))
 		goto error;
 	id = kcontrol->id;
+	if (id.index > UINT_MAX - kcontrol->count)
+		goto error;
+
 	down_write(&card->controls_rwsem);
 	if (snd_ctl_find_id(card, &id)) {
 		up_write(&card->controls_rwsem);
-- 
1.9.1