[PATCH AUTOSEL 4.19 09/14] ALSA: timer: Use deferred fasync helper

[Sasha Levin]

From: Takashi Iwai <tiwai@xxxxxxx>

[ Upstream commit 95cc637c1afd83fb7dd3d7c8a53710488f4caf9c ]

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

Reported-by: syzbot+1ee0910eca9c94f71f25@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+49b10793b867871ee26f@xxxxxxxxxxxxxxxxxxxxxxxxx
Reported-by: syzbot+8285e973a41b5aa68902@xxxxxxxxxxxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/20220728125945.29533-3-tiwai@xxxxxxx
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 sound/core/timer.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/sound/core/timer.c b/sound/core/timer.c
index 4920ec4f4594..f0e8b98f346e 100644
--- a/sound/core/timer.c
+++ b/sound/core/timer.c
@@ -75,7 +75,7 @@ struct snd_timer_user {
 	unsigned int filter;
 	struct timespec tstamp;		/* trigger tstamp */
 	wait_queue_head_t qchange_sleep;
-	struct fasync_struct *fasync;
+	struct snd_fasync *fasync;
 	struct mutex ioctl_lock;
 };
 
@@ -1306,7 +1306,7 @@ static void snd_timer_user_interrupt(struct snd_timer_instance *timeri,
 	}
       __wake:
 	spin_unlock(&tu->qlock);
-	kill_fasync(&tu->fasync, SIGIO, POLL_IN);
+	snd_kill_fasync(tu->fasync, SIGIO, POLL_IN);
 	wake_up(&tu->qchange_sleep);
 }
 
@@ -1343,7 +1343,7 @@ static void snd_timer_user_ccallback(struct snd_timer_instance *timeri,
 	spin_lock_irqsave(&tu->qlock, flags);
 	snd_timer_user_append_to_tqueue(tu, &r1);
 	spin_unlock_irqrestore(&tu->qlock, flags);
-	kill_fasync(&tu->fasync, SIGIO, POLL_IN);
+	snd_kill_fasync(tu->fasync, SIGIO, POLL_IN);
 	wake_up(&tu->qchange_sleep);
 }
 
@@ -1410,7 +1410,7 @@ static void snd_timer_user_tinterrupt(struct snd_timer_instance *timeri,
 	spin_unlock(&tu->qlock);
 	if (append == 0)
 		return;
-	kill_fasync(&tu->fasync, SIGIO, POLL_IN);
+	snd_kill_fasync(tu->fasync, SIGIO, POLL_IN);
 	wake_up(&tu->qchange_sleep);
 }
 
@@ -1476,6 +1476,7 @@ static int snd_timer_user_release(struct inode *inode, struct file *file)
 		if (tu->timeri)
 			snd_timer_close(tu->timeri);
 		mutex_unlock(&tu->ioctl_lock);
+		snd_fasync_free(tu->fasync);
 		kfree(tu->queue);
 		kfree(tu->tqueue);
 		kfree(tu);
@@ -2027,7 +2028,7 @@ static int snd_timer_user_fasync(int fd, struct file * file, int on)
 	struct snd_timer_user *tu;
 
 	tu = file->private_data;
-	return fasync_helper(fd, file, on, &tu->fasync);
+	return snd_fasync_helper(fd, file, on, &tu->fasync);
 }
 
 static ssize_t snd_timer_user_read(struct file *file, char __user *buffer,
-- 
2.35.1