shinys000114/linux
1
0
Fork 0
mirror of https://github.com/hardkernel/linux.git synced 2026-06-04 18:19:28 +09:00
Code Issues Packages Projects Releases Wiki Activity

ALSA: virmidi: Fix too long output trigger loop

Browse Source 
commit 50e9ffb199 upstream.

The virmidi output trigger tries to parse the all available bytes and
process sequencer events as much as possible.  In a normal situation,
this is supposed to be relatively short, but a program may give a huge
buffer and it'll take a long time in a single spin lock, which may
eventually lead to a soft lockup.

This patch simply adds a workaround, a cond_resched() call in the loop
if applicable.  A better solution would be to move the event processor
into a work, but let's put a duct-tape quickly at first.

Reported-and-tested-by: Dae R. Jeong <threeearcat@gmail.com>
Reported-by: syzbot+619d9f40141d826b097e@syzkaller.appspotmail.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai
2018-07-26 14:27:59 +02:00
committed by Greg Kroah-Hartman
parent f13a825ae2
commit f4253b4643
1 changed files with 10 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
sound/core/seq/seq_virmidi.c
View File

@@ -163,6 +163,7 @@ static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream,
int count, res;
unsigned char buf[32], *pbuf;
unsigned long flags;
bool check_resched = !in_atomic();
if (up) {
vmidi->trigger = 1;
@@ -200,6 +201,15 @@ static void snd_virmidi_output_trigger(struct snd_rawmidi_substream *substream,
vmidi->event.type = SNDRV_SEQ_EVENT_NONE;
}
}
if (!check_resched)
continue;
/* do temporary unlock & cond_resched() for avoiding
* CPU soft lockup, which may happen via a write from
* a huge rawmidi buffer
*/
spin_unlock_irqrestore(&substream->runtime->lock, flags);
cond_resched();
spin_lock_irqsave(&substream->runtime->lock, flags);
}
out:
spin_unlock_irqrestore(&substream->runtime->lock, flags);