linux-kernel - [04/17] ALSA: prevent heap corruption in snd_ctl

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Message-Id: <20101022184032.856847478@clark.site>
Date:	Fri, 22 Oct 2010 11:39:29 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Dan Rosenberg <drosenberg@...curity.com>,
	Takashi Iwai <tiwai@...e.de>
Subject: [04/17] ALSA: prevent heap corruption in snd_ctl_new()

2.6.27-stable review patch.  If anyone has any objections, please let us know.

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

From: Dan Rosenberg <drosenberg@...curity.com>

commit 5591bf07225523600450edd9e6ad258bb877b779 upstream.

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@...curity.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 sound/core/control.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/sound/core/control.c
+++ b/sound/core/control.c
@@ -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 */
@@ -190,6 +191,8 @@ static struct snd_kcontrol *snd_ctl_new(
 	
 	snd_assert(control != NULL, return NULL);
 	snd_assert(control->count > 0, 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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