linux-kernel - Re: [syzbot] [net?] WARNING: refcount bug in ethnl_phy

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Message-ID: <20240911120406.123aa4d4@fedora.home>
Date: Wed, 11 Sep 2024 12:04:06 +0200
From: Maxime Chevallier <maxime.chevallier@...tlin.com>
To: syzbot <syzbot+e9ed4e4368d450c8f9db@...kaller.appspotmail.com>
Cc: christophe.leroy@...roup.eu, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
 pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING: refcount bug in ethnl_phy_done

Hi,

On Wed, 11 Sep 2024 01:00:23 -0700
syzbot <syzbot+e9ed4e4368d450c8f9db@...kaller.appspotmail.com> wrote:

> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    a9b1fab3b69f Merge branch 'ionic-convert-rx-queue-buffers-..
> git tree:       net-next
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=1193c49f980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=37742f4fda0d1b09
> dashboard link: https://syzkaller.appspot.com/bug?extid=e9ed4e4368d450c8f9db
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=14bb7bc7980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=17b0a100580000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/0459f959b12d/disk-a9b1fab3.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/337f1be5353b/vmlinux-a9b1fab3.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/0e3701969c4a/bzImage-a9b1fab3.xz
> 
> The issue was bisected to:
> 
> commit 17194be4c8e1e82d8b484e58cdcb495c0714d1fd
> Author: Maxime Chevallier <maxime.chevallier@...tlin.com>
> Date:   Wed Aug 21 15:10:01 2024 +0000
> 
>     net: ethtool: Introduce a command to list PHYs on an interface
> 
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1034a49f980000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=1234a49f980000
> console output: https://syzkaller.appspot.com/x/log.txt?x=1434a49f980000
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e9ed4e4368d450c8f9db@...kaller.appspotmail.com
> Fixes: 17194be4c8e1 ("net: ethtool: Introduce a command to list PHYs on an interface")

I'm currently investigating this. I couldn't reproduce it though, even
with the C reproducer, although this was on an arm64 box. I'll give it
a try on x86_64 with the provided .config, see if I can figure out
what's going on, as it looks like the ethnl_phy_start() doesn't get
called.

Thanks,

Maxime