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

[syzbot <syzbot+332fe1e67018625f63c9@syzkaller.appspotmail.com>]

For archival purposes, forwarding an incoming command email to
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***

Subject: Re: [syzbot] [net?] WARNING in l2tp_exit_net
Author: jchapman@katalix.com

On 06/11/2024 06:00, syzbot wrote:
> syzbot has found a reproducer for the following issue on:
> 
> HEAD commit:    ccb35037c48a Merge branch 'net-lan969x-add-vcap-functional..
> git tree:       net-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=16674f40580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a9d1c42858837b59
> dashboard link: https://syzkaller.appspot.com/bug?extid=332fe1e67018625f63c9
> 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=136a36a7980000
> 
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/4c339ec95c42/disk-ccb35037.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/328f6f24277e/vmlinux-ccb35037.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/0473d4109fcb/bzImage-ccb35037.xz
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+332fe1e67018625f63c9@syzkaller.appspotmail.com
> 
> bond0 (unregistering): (slave bond_slave_0): Releasing backup interface
> bond0 (unregistering): (slave bond_slave_1): Releasing backup interface
> bond0 (unregistering): Released all slaves
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 1153 at net/l2tp/l2tp_core.c:1881 l2tp_exit_net+0x165/0x170 net/l2tp/l2tp_core.c:1881
> Modules linked in:
> CPU: 1 UID: 0 PID: 1153 Comm: kworker/u8:5 Not tainted 6.12.0-rc5-syzkaller-01164-gccb35037c48a #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
> 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 b8 31 a5 f6 eb 05 e8 b1 31 a5 f6 90 0f 0b 90 e9 7a ff ff ff e8 a3 31 a5 f6 eb 05 e8 9c 31 a5 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:ffffc90004177a98 EFLAGS: 00010293
> RAX: ffffffff8aefa87d RBX: ffff888076669088 RCX: ffff8880277abc00
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000002
> RBP: ffffc90004177bb0 R08: ffffffff8bc11bb6 R09: 1ffffffff203a5d5
> R10: dffffc0000000000 R11: fffffbfff203a5d6 R12: dffffc0000000000
> R13: 1ffffffff1fdb678 R14: ffff888076669130 R15: ffff888076669040
> FS:  0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007ffca636d388 CR3: 0000000026e10000 CR4: 00000000003526f0
> 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:633
>   process_one_work kernel/workqueue.c:3229 [inline]
>   process_scheduled_works+0xa63/0x1850 kernel/workqueue.c:3310
>   worker_thread+0x870/0xd30 kernel/workqueue.c:3391
>   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>

Attaching patch for testing.

#syz test: 
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git 
ccb35037c48a