[PATCH v2 3/4] ALSA: pcm: Use deferred fasync helper

[Takashi Iwai <tiwai@suse.de>]

For avoiding the potential deadlock via kill_fasync() call, use the
new fasync helpers to defer the invocation from timer API.  Note that
it's merely a workaround.

Reported-by: syzbot+8285e973a41b5aa68902@syzkaller.appspotmail.com
Reported-by: syzbot+669c9abf11a6a011dd09@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 include/sound/pcm.h     | 2 +-
 sound/core/pcm.c        | 1 +
 sound/core/pcm_lib.c    | 2 +-
 sound/core/pcm_native.c | 2 +-
 4 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 2d03c10f6a36..8c48a5bce88c 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -399,7 +399,7 @@ struct snd_pcm_runtime {
 	snd_pcm_uframes_t twake; 	/* do transfer (!poll) wakeup if non-zero */
 	wait_queue_head_t sleep;	/* poll sleep */
 	wait_queue_head_t tsleep;	/* transfer sleep */
-	struct fasync_struct *fasync;
+	struct snd_fasync *fasync;
 	bool stop_operating;		/* sync_stop will be called */
 	struct mutex buffer_mutex;	/* protect for buffer changes */
 	atomic_t buffer_accessing;	/* >0: in r/w operation, <0: blocked */
diff --git a/sound/core/pcm.c b/sound/core/pcm.c
index 03fc5fa5813e..2ac742035310 100644
--- a/sound/core/pcm.c
+++ b/sound/core/pcm.c
@@ -1007,6 +1007,7 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
 		substream->runtime = NULL;
 	}
 	mutex_destroy(&runtime->buffer_mutex);
+	snd_fasync_free(runtime->fasync);
 	kfree(runtime);
 	put_pid(substream->pid);
 	substream->pid = NULL;
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 1fc7c50ffa62..40751e5aff09 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -1822,7 +1822,7 @@ void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substrea
 		snd_timer_interrupt(substream->timer, 1);
 #endif
  _end:
-	kill_fasync(&runtime->fasync, SIGIO, POLL_IN);
+	snd_kill_fasync(runtime->fasync, SIGIO, POLL_IN);
 }
 EXPORT_SYMBOL(snd_pcm_period_elapsed_under_stream_lock);
 
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index aa0453e51595..ad0541e9e888 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3951,7 +3951,7 @@ static int snd_pcm_fasync(int fd, struct file * file, int on)
 	runtime = substream->runtime;
 	if (runtime->status->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
-	return fasync_helper(fd, file, on, &runtime->fasync);
+	return snd_fasync_helper(fd, file, on, &runtime->fasync);
 }
 
 /*
-- 
2.35.3