Commit 5591bf07 authored Sep 28, 2010 by Dan Rosenberg Committed by Takashi Iwai Sep 28, 2010

ALSA: prevent heap corruption in snd_ctl_new()



The snd_ctl_new() function in sound/core/control.c allocates space for a
snd_kcontrol struct by performing arithmetic operations on a
user-provided size without checking for integer overflow.  If a user
provides a large enough size, an overflow will occur, the allocated
chunk will be too small, and a second user-influenced value will be
written repeatedly past the bounds of this chunk.  This code is
reachable by unprivileged users who have permission to open
a /dev/snd/controlC* device (on many distros, this is group "audio") via
the SNDRV_CTL_IOCTL_ELEM_ADD and SNDRV_CTL_IOCTL_ELEM_REPLACE ioctls.

Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com>
Cc: <stable@kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent e68d3b31

sound/core/control.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -31,6 +31,7 @@

		/* max number of user-defined controls */
		#define MAX_USER_CONTROLS 32
		#define MAX_CONTROL_COUNT 1028

		struct snd_kctl_ioctl {
		struct list_head list; /* list of all ioctls */
		@@ -195,6 +196,10 @@ static struct snd_kcontrol snd_ctl_new(struct snd_kcontrol control,

		if (snd_BUG_ON(!control \|\| !control->count))
		return NULL;

		if (control->count > MAX_CONTROL_COUNT)
		return NULL;

		kctl = kzalloc(sizeof(kctl) + sizeof(struct snd_kcontrol_volatile) control->count, GFP_KERNEL);
		if (kctl == NULL) {
		snd_printk(KERN_ERR "Cannot allocate control instance\n");

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