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    Subject[005/103] ALSA: prevent heap corruption in snd_ctl_new()
    2.6.35-stable review patch.  If anyone has any objections, please let us know.


    From: Dan Rosenberg <>

    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

    Signed-off-by: Dan Rosenberg <>
    Signed-off-by: Takashi Iwai <>
    Signed-off-by: Greg Kroah-Hartman <>

    sound/core/control.c | 5 +++++
    1 file changed, 5 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 */
    @@ -195,6 +196,10 @@ static struct snd_kcontrol *snd_ctl_new(

    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");

     \ /
      Last update: 2010-10-22 20:59    [W:0.024 / U:31.588 seconds]
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