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

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Message-ID: <CANn89iKbof0PsFsPgdhMFeizu9uEkgmqWSQggDQ8EXA5jfxMRg@mail.gmail.com>
Date: Mon, 13 Oct 2025 15:45:17 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: syzbot <syzbot+999eb23467f83f9bf9bf@...kaller.appspotmail.com>
Cc: davem@...emloft.net, 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 xfrm_state_fini (4)

On Sun, Oct 12, 2025 at 2:35 PM syzbot
<syzbot+999eb23467f83f9bf9bf@...kaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    ffce84bccb4d Merge branch 'bpf-avoid-rcu-context-warning-w..
> git tree:       bpf
> console output: https://syzkaller.appspot.com/x/log.txt?x=112559e2580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=1e0e0bf7e51565cd
> dashboard link: https://syzkaller.appspot.com/bug?extid=999eb23467f83f9bf9bf
> 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=1514d304580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/cd489c5f530a/disk-ffce84bc.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/e4a06e8e5022/vmlinux-ffce84bc.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/c1111b7581ab/bzImage-ffce84bc.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+999eb23467f83f9bf9bf@...kaller.appspotmail.com
>
> ------------[ cut here ]------------
> WARNING: CPU: 1 PID: 36 at net/xfrm/xfrm_state.c:3306 xfrm_state_fini+0x26d/0x2f0 net/xfrm/xfrm_state.c:3306
> Modules linked in:
> CPU: 1 UID: 0 PID: 36 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
> Workqueue: netns cleanup_net
> RIP: 0010:xfrm_state_fini+0x26d/0x2f0 net/xfrm/xfrm_state.c:3306
> Code: c1 e8 03 42 80 3c 28 00 74 08 48 89 df e8 4b f0 36 f8 48 8b 3b 5b 41 5c 41 5d 41 5e 41 5f 5d e9 99 e1 16 f8 e8 64 4d d1 f7 90 <0f> 0b 90 e9 fd fd ff ff e8 56 4d d1 f7 90 0f 0b 90 e9 60 fe ff ff
> RSP: 0018:ffffc90000ac7878 EFLAGS: 00010293
> RAX: ffffffff89edd6ec RBX: ffff888058e08000 RCX: ffff88801ce99e40
> RDX: 0000000000000000 RSI: ffffffff8d9cc7ae RDI: ffff88801ce99e40
> RBP: ffffc90000ac7990 R08: ffffffff8f9db437 R09: 1ffffffff1f3b686
> R10: dffffc0000000000 R11: fffffbfff1f3b687 R12: ffffffff8f5d4bc0
> R13: 1ffff92000158f3c R14: ffff888058e094c0 R15: dffffc0000000000
> FS:  0000000000000000(0000) GS:ffff888125e27000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007eff78efa6b0 CR3: 000000007788c000 CR4: 00000000003526f0
> Call Trace:
>  <TASK>
>  xfrm_net_exit+0x2d/0x70 net/xfrm/xfrm_policy.c:4354
>  ops_exit_list net/core/net_namespace.c:199 [inline]
>  ops_undo_list+0x497/0x990 net/core/net_namespace.c:252
>  cleanup_net+0x4d8/0x820 net/core/net_namespace.c:695
>  process_one_work kernel/workqueue.c:3263 [inline]
>  process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3346
>  worker_thread+0x8a0/0xda0 kernel/workqueue.c:3427
>  kthread+0x70e/0x8a0 kernel/kthread.c:463
>  ret_from_fork+0x4bc/0x870 arch/x86/kernel/process.c:148
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>  </TASK>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
> syzbot engineers can be reached at syzkaller@...glegroups.com.
>
> syzbot will keep track of this issue. See:
> https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
>
> If the report is already addressed, let syzbot know by replying with:
> #syz fix: exact-commit-title
>
> 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.
>
> If you want to overwrite report's subsystems, reply with:
> #syz set subsystems: new-subsystem
> (See the list of subsystem names on the web dashboard)
>
> If the report is a duplicate of another one, reply with:
> #syz dup: exact-subject-of-another-report
>
> If you want to undo deduplication, reply with:
> #syz undup

#syz test

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 95241093b7f0..17240503a366 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1744,6 +1744,8 @@ int __udp_enqueue_schedule_skb(struct sock *sk,
struct sk_buff *skb)

        atomic_add(size, &udp_prod_queue->rmem_alloc);

+       secpath_reset(skb);
+
        if (!llist_add(&skb->ll_node, &udp_prod_queue->ll_root))
                return 0;