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ALSA: seq: Cover unsubscribe_port() in list_mutex

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commit 7c32ae35fb upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Takashi Iwai
2019-04-12 11:37:19 +02:00
committed by Greg Kroah-Hartman
parent 5e0c41ca89
commit cb0c8bbd9d
1 changed files with 1 additions and 1 deletions
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2
sound/core/seq/seq_ports.c
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@@ -550,10 +550,10 @@ 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 */