From 7c32ae35fbf9cffb7aa3736f44dec10c944ca18e Mon Sep 17 00:00:00 2001
From: Takashi Iwai <tiwai@suse.de>
Date: Fri, 12 Apr 2019 11:37:19 +0200
Subject: [PATCH] ALSA: seq: Cover unsubscribe_port() in list_mutex
Git-commit: 7c32ae35fbf9cffb7aa3736f44dec10c944ca18e
Patch-mainline: v5.2-rc1
References: bsc#1051510
The call of unsubscribe_port() which manages the group count and
module refcount from delete_and_unsubscribe_port() looks racy; it's
not covered by the group list lock, and it's likely a cause of the
reported unbalance at port deletion. Let's move the call inside the
group list_mutex to plug the hole.
Reported-by: syzbot+e4c8abb920efa77bace9@syzkaller.appspotmail.com
Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
sound/core/seq/seq_ports.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/sound/core/seq/seq_ports.c b/sound/core/seq/seq_ports.c
index d964d728681e..ac7556ab531c 100644
--- a/sound/core/seq/seq_ports.c
+++ b/sound/core/seq/seq_ports.c
@@ -547,10 +547,10 @@ static void delete_and_unsubscribe_port(struct snd_seq_client *client,
list_del_init(list);
grp->exclusive = 0;
write_unlock_irq(&grp->list_lock);
- up_write(&grp->list_mutex);
if (!empty)
unsubscribe_port(client, port, grp, &subs->info, ack);
+ up_write(&grp->list_mutex);
}
/* connect two ports */
--
2.16.4