Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 82fd4b05 authored by Takashi Iwai's avatar Takashi Iwai
Browse files

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: f7debfe5 ("ALSA: seq: virmidi: Offload the output event processing")
Reported-by: default avatar <syzbot+ec5f605c91812d200367@syzkaller.appspotmail.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent f5b6c1fc

sound/core/seq/seq_virmidi.c

+3 −2
Original line number Diff line number Diff line
@@ -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 */

		return;

	}