path: root/sound
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authorTakashi Iwai <tiwai@suse.de>2018-08-14 21:27:51 +0200
committerTakashi Iwai <tiwai@suse.de>2018-08-14 22:50:52 +0200
commit82fd4b05d704623a0e4aa7fda48e272a9889337d (patch)
tree711f3d02a97fcfb7231193c85b49a976aa07b5a1 /sound
parentf5b6c1fcb42fe7d6f2f6eb2220512e2a5f875133 (diff)
ALSA: seq: virmidi: Fix discarding the unsubscribed output
The recent change to move the virmidi output processing to a work slightly modified the code to discard the unsubscribed outputs so that it works without a temporary buffer. However, this is actually buggy, and may spew a kernel warning due to the unexpected call of snd_rawmidi_transmit_ack(), as triggered by syzbot. This patch takes back to the original code in that part, use a temporary buffer and simply repeat snd_rawmidi_transmit(), in order to address the regression. Fixes: f7debfe54090 ("ALSA: seq: virmidi: Offload the output event processing") Reported-by: syzbot+ec5f605c91812d200367@syzkaller.appspotmail.com Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'sound')
1 files changed, 3 insertions, 2 deletions
diff --git a/sound/core/seq/seq_virmidi.c b/sound/core/seq/seq_virmidi.c
index a2f1c6b58693..cb988efd1ed0 100644
--- a/sound/core/seq/seq_virmidi.c
+++ b/sound/core/seq/seq_virmidi.c
@@ -149,8 +149,9 @@ static void snd_vmidi_output_work(struct work_struct *work)
/* discard the outputs in dispatch mode unless subscribed */
if (vmidi->seq_mode == SNDRV_VIRMIDI_SEQ_DISPATCH &&
!(vmidi->rdev->flags & SNDRV_VIRMIDI_SUBSCRIBE)) {
- while (!snd_rawmidi_transmit_empty(substream))
- snd_rawmidi_transmit_ack(substream, 1);
+ char buf[32];
+ while (snd_rawmidi_transmit(substream, buf, sizeof(buf)) > 0)
+ ; /* ignored */