[Lucid][CVE-2014-4656 2/2] ALSA: control: Make sure that id->index does not overflow

[Luis Henriques]

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

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>
Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
(cherry picked from commit 883a1d49f0d77d30012f114b2e19fc141beb3e8e)
CVE-2014-4656
BugLink: http://bugs.launchpad.net/bugs/1339306
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 acd92ffb2bc2..8b1f46c68a86 100644
--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -333,6 +333,9 @@ 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