ALSA: echoaudio: Prevent races in calls to set_audio_format()

The function uses chip->comm_page which needs locking against
other use at the same time.

Signed-off-by: Mark Hills <mark@xwax.org>
Link: https://lore.kernel.org/r/20200708101848.3457-3-mark@xwax.org
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --git a/sound/pci/echoaudio/echoaudio.c b/sound/pci/echoaudio/echoaudio.c
index f2bc37c..c97928e 100644 (file)
--- a/sound/pci/echoaudio/echoaudio.c
+++ b/sound/pci/echoaudio/echoaudio.c
@@ -711,9 +711,22 @@ static int pcm_prepare(struct snd_pcm_substream *substream)
 
        if (snd_BUG_ON(pipe_index >= px_num(chip)))
                return -EINVAL;
-       if (snd_BUG_ON(!is_pipe_allocated(chip, pipe_index)))
+
+       /*
+        * We passed checks we can do independently; now take
+        * exclusive control
+        */
+
+       spin_lock_irq(&chip->lock);
+
+       if (snd_BUG_ON(!is_pipe_allocated(chip, pipe_index))) {
+               spin_unlock(&chip->lock);
                return -EINVAL;
+       }
+
        set_audio_format(chip, pipe_index, &format);
+       spin_unlock_irq(&chip->lock);
+
        return 0;
 }