Subject: [syzbot] [net?] WARNING in l2tp_exit_net

From: syzbot <[email-masked]>
Date: Thu, 12 Sep 2024 19:49:24 -0700

Hello,

syzbot found the following issue on:

HEAD commit:    f3b6129b7d25 Merge branch '100GbE' of git://git.kernel.org..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=144ba477980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=37742f4fda0d1b09
dashboard link: https://syzkaller.appspot.com/bug?extid=332fe1e67018625f63c9
compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a742e7b2e0d2/disk-f3b6129b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6982186745fb/vmlinux-f3b6129b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5fd38b217bb5/bzImage-f3b6129b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email-masked]

bond0 (unregistering): (slave dummy0): Releasing backup interface
bond0 (unregistering): Released all slaves
tipc: Disabling bearer <eth:batadv0>
tipc: Disabling bearer <udp:syz0>
tipc: Left network mode
------------[ cut here ]------------
WARNING: CPU: 0 PID: 17026 at net/l2tp/l2tp_core.c:1881 l2tp_exit_net+0x165/0x170 net/l2tp/l2tp_core.c:1881
Modules linked in:
CPU: 0 UID: 0 PID: 17026 Comm: kworker/u8:36 Not tainted 6.11.0-rc6-syzkaller-01324-gf3b6129b7d25 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Workqueue: netns cleanup_net
RIP: 0010:l2tp_exit_net+0x165/0x170 net/l2tp/l2tp_core.c:1881
Code: 0f 0b 90 e9 3b ff ff ff e8 48 a4 b0 f6 eb 05 e8 41 a4 b0 f6 90 0f 0b 90 e9 7a ff ff ff e8 33 a4 b0 f6 eb 05 e8 2c a4 b0 f6 90 <0f> 0b 90 eb b5 66 0f 1f 44 00 00 90 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc9000ae07a98 EFLAGS: 00010293
RAX: ffffffff8ae2e87d RBX: ffff8880797c0888 RCX: ffff88806dbbda00
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
RBP: ffffc9000ae07bb0 R08: ffffffff8bb2ce16 R09: 1ffffffff2031025
R10: dffffc0000000000 R11: fffffbfff2031026 R12: dffffc0000000000
R13: 1ffffffff1fd274c R14: ffff8880797c0930 R15: ffff8880797c0840
FS:  0000000000000000(0000) GS:ffff8880b8800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c3831d6 CR3: 000000000e734000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 ops_exit_list net/core/net_namespace.c:173 [inline]
 cleanup_net+0x802/0xcc0 net/core/net_namespace.c:626
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312
 worker_thread+0x86d/0xd10 kernel/workqueue.c:3389
 kthread+0x2f0/0x390 kernel/kthread.c:389
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

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