netdev - Re: [syzbot] [netfilter?] possible deadlock in nf_tables_dumpreset

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Message-ID: <aVuBFErrvyjKv0v5@strlen.de>
Date: Mon, 5 Jan 2026 10:15:00 +0100
From: Florian Westphal <fw@...len.de>
To: syzbot <syzbot+ee287f5effa60050d9ac@...kaller.appspotmail.com>
Cc: coreteam@...filter.org, davem@...emloft.net, edumazet@...gle.com,
	horms@...nel.org, kadlec@...filter.org, kuba@...nel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	netfilter-devel@...r.kernel.org, pabeni@...hat.com,
	pablo@...filter.org, phil@....cc, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [netfilter?] possible deadlock in
 nf_tables_dumpreset_rules

syzbot <syzbot+ee287f5effa60050d9ac@...kaller.appspotmail.com> wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    54e82e93ca93 Merge tag 'core_urgent_for_v6.19_rc4' of git:..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=10b1ee22580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=8bfa57a8c0ab3aa8
> dashboard link: https://syzkaller.appspot.com/bug?extid=ee287f5effa60050d9ac
> compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: i386
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-54e82e93.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/c7af41d4f0f4/vmlinux-54e82e93.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/02aa2250dd4f/bzImage-54e82e93.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+ee287f5effa60050d9ac@...kaller.appspotmail.com
> 
> netlink: 48 bytes leftover after parsing attributes in process `syz.8.6539'.
> ======================================================
> WARNING: possible circular locking dependency detected
> syzkaller #0 Tainted: G             L     
> ------------------------------------------------------
> syz.8.6539/2008 is trying to acquire lock:
> ffff888052e32cd8 (&nft_net->commit_mutex){+.+.}-{4:4}, at: nf_tables_dumpreset_rules+0x6f/0xa0 net/netfilter/nf_tables_api.c:3913
> 
> but task is already holding lock:
> ffff888025cb16f0 (nlk_cb_mutex-NETFILTER){+.+.}-{4:4}, at: __netlink_dump_start+0x150/0x990 net/netlink/af_netlink.c:2404
 
> which lock already depends on the new lock.

#syz dup: possible deadlock in nf_tables_dumpreset_obj