ALSA: aloop: Add missing cable lock to ctl API callbacks

Some control API callbacks in aloop driver are too lazy to take the
loopback->cable_lock and it results in possible races of cable access
while it's being freed.  It eventually lead to a UAF, as reported by
fuzzer recently.

This patch covers such control API callbacks and add the proper mutex
locks.

Reported-by: DaeRyong Jeong <threeearcat@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 15 insertions, 2 deletions

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 58e349fc893f..eab7f594ebe7 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -831,9 +831,11 @@ static int loopback_rate_shift_get(struct snd_kcontrol *kcontrol,
 {
         struct loopback *loopback = snd_kcontrol_chip(kcontrol);
         
+        mutex_lock(&loopback->cable_lock);
         ucontrol->value.integer.value[0] =
                 loopback->setup[kcontrol->id.subdevice]
                                [kcontrol->id.device].rate_shift;
+        mutex_unlock(&loopback->cable_lock);
         return 0;
 }
 
@@ -865,9 +867,11 @@ static int loopback_notify_get(struct snd_kcontrol *kcontrol,
 {
         struct loopback *loopback = snd_kcontrol_chip(kcontrol);
         
+        mutex_lock(&loopback->cable_lock);
         ucontrol->value.integer.value[0] =
                 loopback->setup[kcontrol->id.subdevice]
                                [kcontrol->id.device].notify;
+        mutex_unlock(&loopback->cable_lock);
         return 0;
 }
 
@@ -879,12 +883,14 @@ static int loopback_notify_put(struct snd_kcontrol *kcontrol,
         int change = 0;
 
         val = ucontrol->value.integer.value[0] ? 1 : 0;
+        mutex_lock(&loopback->cable_lock);
         if (val != loopback->setup[kcontrol->id.subdevice]
                                 [kcontrol->id.device].notify) {
                 loopback->setup[kcontrol->id.subdevice]
                         [kcontrol->id.device].notify = val;
                 change = 1;
         }
+        mutex_unlock(&loopback->cable_lock);
         return change;
 }
 
@@ -892,15 +898,18 @@ static int loopback_active_get(struct snd_kcontrol *kcontrol,
                                struct snd_ctl_elem_value *ucontrol)
 {
         struct loopback *loopback = snd_kcontrol_chip(kcontrol);
-        struct loopback_cable *cable = loopback->cables
-                        [kcontrol->id.subdevice][kcontrol->id.device ^ 1];
+        struct loopback_cable *cable;
+
         unsigned int val = 0;
 
+        mutex_lock(&loopback->cable_lock);
+        cable = loopback->cables[kcontrol->id.subdevice][kcontrol->id.device ^ 1];
         if (cable != NULL) {
                 unsigned int running = cable->running ^ cable->pause;
 
                 val = (running & (1 << SNDRV_PCM_STREAM_PLAYBACK)) ? 1 : 0;
         }
+        mutex_unlock(&loopback->cable_lock);
         ucontrol->value.integer.value[0] = val;
         return 0;
 }
@@ -943,9 +952,11 @@ static int loopback_rate_get(struct snd_kcontrol *kcontrol,
 {
         struct loopback *loopback = snd_kcontrol_chip(kcontrol);
         
+        mutex_lock(&loopback->cable_lock);
         ucontrol->value.integer.value[0] =
                 loopback->setup[kcontrol->id.subdevice]
                                [kcontrol->id.device].rate;
+        mutex_unlock(&loopback->cable_lock);
         return 0;
 }
 
@@ -965,9 +976,11 @@ static int loopback_channels_get(struct snd_kcontrol *kcontrol,
 {
         struct loopback *loopback = snd_kcontrol_chip(kcontrol);
         
+        mutex_lock(&loopback->cable_lock);
         ucontrol->value.integer.value[0] =
                 loopback->setup[kcontrol->id.subdevice]
                                [kcontrol->id.device].channels;
+        mutex_unlock(&loopback->cable_lock);
         return 0;
 }