[alsa-devel] [PATCH 1/8] ALSA: seq: oss: Fix unbalanced use lock for synth MIDI device

[Takashi Iwai]

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.

Cc: <stable at vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai at suse.de>
---
 sound/core/seq/oss/seq_oss_synth.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/sound/core/seq/oss/seq_oss_synth.c b/sound/core/seq/oss/seq_oss_synth.c
index cd0e0ebbfdb1..9e2b250ae780 100644
--- 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;
-- 
2.16.3