linux-kernel - Re: WARNING in port

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Date:   Tue, 24 Jul 2018 09:00:55 +0200
From:   Takashi Iwai <tiwai@...e.de>
To:     "DaeRyong Jeong" <threeearcat@...il.com>
Cc:     "Colin King" <colin.king@...onical.com>, <perex@...ex.cz>,
        <alsa-devel@...a-project.org>, "Kyungtae Kim" <kt0755@...il.com>,
        "Byoungyoung Lee" <lifeasageek@...il.com>,
        <syzkaller@...glegroups.com>, <bammanag@...due.edu>,
        "LKML" <linux-kernel@...r.kernel.org>
Subject: Re: WARNING in port_delete

On Tue, 24 Jul 2018 05:59:56 +0200,
DaeRyong Jeong wrote:
> 
> I just realized that the crash has been spotted by Syzkaller a few days before.
> (https://syzkaller.appspot.com/bug?id=3490860a465e6b39227c6906f0ef2d40ad4d5bb1)
> 
> I'm CC'ing Syzkaller's mailing list.

It's very likely a false-positive sanity check, and if so, nothing
serious at all.  We may simply remove two snd_BUG_ON() lines.

But I'd love to have a C reproducer to confirm my understanding is
correct...


thanks,

Takashi

---
--- a/sound/core/seq/seq_ports.c
+++ b/sound/core/seq/seq_ports.c
@@ -272,9 +272,6 @@ static int port_delete(struct snd_seq_client *client,
 	if (port->private_free)
 		port->private_free(port->private_data);
 
-	snd_BUG_ON(port->c_src.count != 0);
-	snd_BUG_ON(port->c_dest.count != 0);
-
 	kfree(port);
 	return 0;
 }