ALSA: seq: oss: Fix unbalanced use lock for synth MIDI device

commit f5e94b4c6ebdabe0f602d796e0430180927521a0 upstream.

When get_synthdev() is called for a MIDI device, it returns the fixed
midi_synth_dev without the use refcounting.  OTOH, the caller is
supposed to unreference unconditionally after the usage, so this would
lead to unbalanced refcount.

This patch corrects the behavior and keep up the refcount balance also
for the MIDI synth device.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/sound/core/seq/oss/seq_oss_synth.c b/sound/core/seq/oss/seq_oss_synth.c
index ac3d7d2125e992fb81a31e2a14900582e3a9fb05..760b340921103bc09661ead337ba01a43d4eae7f 100644 (file)
--- a/sound/core/seq/oss/seq_oss_synth.c
+++ b/sound/core/seq/oss/seq_oss_synth.c
@@ -363,10 +363,14 @@ get_synthdev(struct seq_oss_devinfo *dp, int dev)
                return NULL;
        if (! dp->synths[dev].opened)
                return NULL;
-       if (dp->synths[dev].is_midi)
-               return &midi_synth_dev;
-       if ((rec = get_sdev(dev)) == NULL)
-               return NULL;
+       if (dp->synths[dev].is_midi) {
+               rec = &midi_synth_dev;
+               snd_use_lock_use(&rec->use_lock);
+       } else {
+               rec = get_sdev(dev);
+               if (!rec)
+                       return NULL;
+       }
        if (! rec->opened) {
                snd_use_lock_free(&rec->use_lock);
                return NULL;