[PATCH 3.2 087/125] ALSA: control: Make sure that id->index does not overflow

[Ben Hutchings]

3.2.61-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

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@xxxxxxxxxx>
Acked-by: Jaroslav Kysela <perex@xxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 sound/core/control.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -341,6 +341,9 @@ int snd_ctl_add(struct snd_card *card, s
 	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);

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