ALSA: snd-usb-us122l: Fix missing NULL checks

Fix missing NULL checks in usb_stream_hwdep_poll() and usb_stream_hwdep_ioctl().
Wake up poll waiters before returning from usb_stream_hwdep_ioctl().
Signed-off-by: Karsten Wiese <fzu@wemgehoertderstaat.de>
Cc: stable@kernel.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/usx2y/us122l.c

@@ -273,14 +273,15 @@ static unsigned int usb_stream_hwdep_poll(struct snd_hwdep *hw,
 					  struct file *file, poll_table *wait)
 {
 	struct us122l	*us122l = hw->private_data;
-	struct usb_stream *s = us122l->sk.s;
 	unsigned	*polled;
 	unsigned int	mask;
 
 	poll_wait(file, &us122l->sk.sleep, wait);
 
-	switch (s->state) {
-	case usb_stream_ready:
+	mask = POLLIN | POLLOUT | POLLWRNORM | POLLERR;
+	if (mutex_trylock(&us122l->mutex)) {
+		struct usb_stream *s = us122l->sk.s;
+		if (s && s->state == usb_stream_ready) {
 			if (us122l->first == file)
 				polled = &s->periods_polled;
 			else
@@ -288,14 +289,10 @@ static unsigned int usb_stream_hwdep_poll(struct snd_hwdep *hw,
 			if (*polled != s->periods_done) {
 				*polled = s->periods_done;
 				mask = POLLIN | POLLOUT | POLLWRNORM;
-			break;
-		}
-		/* Fall through */
+			} else
 				mask = 0;
-		break;
-	default:
-		mask = POLLIN | POLLOUT | POLLWRNORM | POLLERR;
-		break;
+		}
+		mutex_unlock(&us122l->mutex);
 	}
 	return mask;
 }
@@ -381,6 +378,7 @@ static int usb_stream_hwdep_ioctl(struct snd_hwdep *hw, struct file *file,
 {
 	struct usb_stream_config *cfg;
 	struct us122l *us122l = hw->private_data;
+	struct usb_stream *s;
 	unsigned min_period_frames;
 	int err = 0;
 	bool high_speed;
@@ -426,18 +424,18 @@ static int usb_stream_hwdep_ioctl(struct snd_hwdep *hw, struct file *file,
 	snd_power_wait(hw->card, SNDRV_CTL_POWER_D0);
 
 	mutex_lock(&us122l->mutex);
+	s = us122l->sk.s;
 	if (!us122l->master)
 		us122l->master = file;
 	else if (us122l->master != file) {
-		if (memcmp(cfg, &us122l->sk.s->cfg, sizeof(*cfg))) {
+		if (!s || memcmp(cfg, &s->cfg, sizeof(*cfg))) {
 			err = -EIO;
 			goto unlock;
 		}
 		us122l->slave = file;
 	}
-	if (!us122l->sk.s ||
-	    memcmp(cfg, &us122l->sk.s->cfg, sizeof(*cfg)) ||
-	    us122l->sk.s->state == usb_stream_xrun) {
+	if (!s || memcmp(cfg, &s->cfg, sizeof(*cfg)) ||
+	    s->state == usb_stream_xrun) {
 		us122l_stop(us122l);
 		if (!us122l_start(us122l, cfg->sample_rate, cfg->period_frames))
 			err = -EIO;
@@ -448,6 +446,7 @@ static int usb_stream_hwdep_ioctl(struct snd_hwdep *hw, struct file *file,
 	mutex_unlock(&us122l->mutex);
 free:
 	kfree(cfg);
+	wake_up_all(&us122l->sk.sleep);
 	return err;
 }