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authorTakashi Iwai <tiwai@suse.de>2020-06-24 15:23:40 +0300
committerTakashi Iwai <tiwai@suse.de>2020-06-24 15:24:29 +0300
commit220345e98f1cdc768eeb6e3364a0fa7ab9647fe7 (patch)
treec3fd3927a037edc80b7ec782cd15e390089168fd /sound/usb/mixer.c
parenta32a1fc99807244d920d274adc46ba04b538cc8a (diff)
downloadlinux-220345e98f1cdc768eeb6e3364a0fa7ab9647fe7.tar.xz
ALSA: usb-audio: Fix OOB access of mixer element list
The USB-audio mixer code holds a linked list of usb_mixer_elem_list, and several operations are performed for each mixer element. A few of them (snd_usb_mixer_notify_id() and snd_usb_mixer_interrupt_v2()) assume each mixer element being a usb_mixer_elem_info object that is a subclass of usb_mixer_elem_list, cast via container_of() and access it members. This may result in an out-of-bound access when a non-standard list element has been added, as spotted by syzkaller recently. This patch adds a new field, is_std_info, in usb_mixer_elem_list to indicate that the element is the usb_mixer_elem_info type or not, and skip the access to such an element if needed. Reported-by: syzbot+fb14314433463ad51625@syzkaller.appspotmail.com Reported-by: syzbot+2405ca3401e943c538b5@syzkaller.appspotmail.com Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20200624122340.9615-1-tiwai@suse.de Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound/usb/mixer.c')
-rw-r--r--sound/usb/mixer.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
index 15769f266790..eab0fd4fd7c3 100644
--- a/sound/usb/mixer.c
+++ b/sound/usb/mixer.c
@@ -581,8 +581,9 @@ static int check_matrix_bitmap(unsigned char *bmap,
* if failed, give up and free the control instance.
*/
-int snd_usb_mixer_add_control(struct usb_mixer_elem_list *list,
- struct snd_kcontrol *kctl)
+int snd_usb_mixer_add_list(struct usb_mixer_elem_list *list,
+ struct snd_kcontrol *kctl,
+ bool is_std_info)
{
struct usb_mixer_interface *mixer = list->mixer;
int err;
@@ -596,6 +597,7 @@ int snd_usb_mixer_add_control(struct usb_mixer_elem_list *list,
return err;
}
list->kctl = kctl;
+ list->is_std_info = is_std_info;
list->next_id_elem = mixer->id_elems[list->id];
mixer->id_elems[list->id] = list;
return 0;
@@ -3234,8 +3236,11 @@ void snd_usb_mixer_notify_id(struct usb_mixer_interface *mixer, int unitid)
unitid = delegate_notify(mixer, unitid, NULL, NULL);
for_each_mixer_elem(list, mixer, unitid) {
- struct usb_mixer_elem_info *info =
- mixer_elem_list_to_info(list);
+ struct usb_mixer_elem_info *info;
+
+ if (!list->is_std_info)
+ continue;
+ info = mixer_elem_list_to_info(list);
/* invalidate cache, so the value is read from the device */
info->cached = 0;
snd_ctl_notify(mixer->chip->card, SNDRV_CTL_EVENT_MASK_VALUE,
@@ -3315,6 +3320,8 @@ static void snd_usb_mixer_interrupt_v2(struct usb_mixer_interface *mixer,
if (!list->kctl)
continue;
+ if (!list->is_std_info)
+ continue;
info = mixer_elem_list_to_info(list);
if (count > 1 && info->control != control)