ALSA: firewire-tascam: handle error code when getting current source of clock

BugLink: https://bugs.launchpad.net/bugs/1848589

commit 2617120f upstream.

The return value of snd_tscm_stream_get_clock() is ignored. This commit
checks the value and handle error.

Fixes: e453df44 ("ALSA: firewire-tascam: add PCM functionality")
Cc: <stable@vger.kernel.org> # v4.4+
Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Link: https://lore.kernel.org/r/20190910135152.29800-2-o-takashi@sakamocchi.jpSigned-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

sound/firewire/tascam/tascam-pcm.c

@@ -81,6 +81,9 @@ static int pcm_open(struct snd_pcm_substream *substream)
 		goto err_locked;
 
 	err = snd_tscm_stream_get_clock(tscm, &clock);
+	if (err < 0)
+		goto err_locked;
+
 	if (clock != SND_TSCM_CLOCK_INTERNAL ||
 	    amdtp_stream_pcm_running(&tscm->rx_stream) ||
 	    amdtp_stream_pcm_running(&tscm->tx_stream)) {