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>

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 58e349fc893f3815904aa0d85244bc4e4d6e9232..eab7f594ebe7599d74aee47129cbb51047549286 100644 (file)
--- 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;
 }