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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>
Dan Rosenberg 15 years ago
parent
commit
5591bf0722
1 changed files with 5 additions and 0 deletions
  1. 5 0
      sound/core/control.c

+ 5 - 0
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 */
@@ -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");