linux-kernel - Re: [syzbot] [net?] WARNING in xfrm6_tunnel_net

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Message-ID: <68f3707c.050a0220.1186a4.051f.GAE@google.com>
Date: Sat, 18 Oct 2025 03:48:28 -0700
From: syzbot <syzbot+3df59a64502c71cab3d5@...kaller.appspotmail.com>
To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	herbert@...dor.apana.org.au, horms@...nel.org, kuba@...nel.org, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, 
	steffen.klassert@...unet.com, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [net?] WARNING in xfrm6_tunnel_net_exit (4)

syzbot has found a reproducer for the following issue on:

HEAD commit:    cf1ea8854e4f Merge tag 'mmc-v6.18-rc1' of git://git.kernel..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14b96492580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=af9170887d81dea1
dashboard link: https://syzkaller.appspot.com/bug?extid=3df59a64502c71cab3d5
compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=162c3de2580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a6a5b37662b9/disk-cf1ea885.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4b4d732ae480/vmlinux-cf1ea885.xz
kernel image: https://storage.googleapis.com/syzbot-assets/acd7feec5537/bzImage-cf1ea885.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+3df59a64502c71cab3d5@...kaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 12 at net/ipv6/xfrm6_tunnel.c:341 xfrm6_tunnel_net_exit+0x7e/0x100 net/ipv6/xfrm6_tunnel.c:341
Modules linked in:
CPU: 0 UID: 0 PID: 12 Comm: kworker/u8:0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: netns cleanup_net
RIP: 0010:xfrm6_tunnel_net_exit+0x7e/0x100 net/ipv6/xfrm6_tunnel.c:341
Code: e8 66 90 f8 4b 83 3c 2c 00 75 19 e8 dc b4 2e f8 49 81 fd f8 07 00 00 74 1d e8 ce b4 2e f8 49 83 c5 08 eb c9 e8 c3 b4 2e f8 90 <0f> 0b 90 49 81 fd f8 07 00 00 75 e3 48 81 c3 00 08 00 00 45 31 f6
RSP: 0018:ffffc90000117890 EFLAGS: 00010293
RAX: ffffffff8990486d RBX: ffff888030f5c000 RCX: ffff88801ba9da00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90000117990 R08: 0000000000000000 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff1deee6f R12: ffff888030f5c000
R13: 00000000000003f0 R14: ffff888038a38000 R15: dffffc0000000000
FS:  0000000000000000(0000) GS:ffff888126bc6000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fd8ab2e0890 CR3: 00000000338be000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 ops_exit_list net/core/net_namespace.c:199 [inline]
 ops_undo_list+0x49a/0x990 net/core/net_namespace.c:252
 cleanup_net+0x4de/0x820 net/core/net_namespace.c:695
 process_one_work kernel/workqueue.c:3263 [inline]
 process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3346
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.