This is a note to let you know that I've just added the patch titled
ALSA: pcm : Call kill_fasync() in stream lock
to the 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
alsa-pcm-call-kill_fasync-in-stream-lock.patch
and it can be found in the queue-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3aa02cb664c5fb1042958c8d1aa8c35055a2ebc4 Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@xxxxxxx>
Date: Thu, 14 Apr 2016 18:02:37 +0200
Subject: ALSA: pcm : Call kill_fasync() in stream lock
From: Takashi Iwai <tiwai@xxxxxxx>
commit 3aa02cb664c5fb1042958c8d1aa8c35055a2ebc4 upstream.
Currently kill_fasync() is called outside the stream lock in
snd_pcm_period_elapsed(). This is potentially racy, since the stream
may get released even during the irq handler is running. Although
snd_pcm_release_substream() calls snd_pcm_drop(), this doesn't
guarantee that the irq handler finishes, thus the kill_fasync() call
outside the stream spin lock may be invoked after the substream is
detached, as recently reported by KASAN.
As a quick workaround, move kill_fasync() call inside the stream
lock. The fasync is rarely used interface, so this shouldn't have a
big impact from the performance POV.
Ideally, we should implement some sync mechanism for the proper finish
of stream and irq handler. But this oneliner should suffice for most
cases, so far.
Reported-by: Baozeng Ding <sploving1@xxxxxxxxx>
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
sound/core/pcm_lib.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1858,10 +1858,10 @@ void snd_pcm_period_elapsed(struct snd_p
if (substream->timer_running)
snd_timer_interrupt(substream->timer, 1);
_end:
+ kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
snd_pcm_stream_unlock_irqrestore(substream, flags);
if (runtime->transfer_ack_end)
runtime->transfer_ack_end(substream);
- kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
}
EXPORT_SYMBOL(snd_pcm_period_elapsed);
Patches currently in stable-queue which might be from tiwai@xxxxxxx are
queue-3.18/alsa-ppc-awacs-shut-up-maybe-uninitialized-warning.patch
queue-3.18/alsa-seq-don-t-break-snd_use_lock_sync-loop-by-timeout.patch
queue-3.18/alsa-pcm-call-kill_fasync-in-stream-lock.patch