[v6.1] WARNING: refcount bug in skb_expand_head

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 88690811da69 Linux 6.1.92
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=112110ee980000
kernel config: https://syzkaller.appspot.com/x/.config?x=ee57a613e7f5bf6c
dashboard link: https://syzkaller.appspot.com/bug?extid=5548b221da2a8515ba2a
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/8b45ba80e02a/disk-88690811.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ca769d644800/vmlinux-88690811.xz
kernel image: https://storage.googleapis.com/syzbot-assets/26a1d8aecbf6/bzImage-88690811.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+5548b2...@syzkaller.appspotmail.com

------------[ cut here ]------------
refcount_t: saturated; leaking memory.
WARNING: CPU: 0 PID: 3852 at lib/refcount.c:22 refcount_warn_saturate+0x116/0x1a0 lib/refcount.c:22
Modules linked in:
CPU: 0 PID: 3852 Comm: kworker/0:10 Not tainted 6.1.92-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Workqueue: wg-crypt-wg2 wg_packet_tx_worker
RIP: 0010:refcount_warn_saturate+0x116/0x1a0 lib/refcount.c:22
Code: 0a 01 48 c7 c7 80 0a 3d 8b e8 36 3f 1a fd 0f 0b eb c5 e8 2d 40 52 fd c6 05 c3 44 27 0a 01 48 c7 c7 00 09 3d 8b e8 1a 3f 1a fd <0f> 0b eb a9 e8 11 40 52 fd c6 05 a8 44 27 0a 01 48 c7 c7 60 09 3d
RSP: 0018:ffffc90013be7730 EFLAGS: 00010246
RAX: d19bdc3c4700e000 RBX: 0000000000000001 RCX: ffff888022b6d940
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffffff81528ede R09: fffff5200277ce45
R10: 0000000000000000 R11: dffffc0000000001 R12: dffffc0000000000
R13: ffff88802154d234 R14: 0000000000200000 R15: ffff88807b75edc0
FS: 0000000000000000(0000) GS:ffff8880b9800000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b2fe28000 CR3: 000000000ce8e000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
refcount_add include/linux/refcount.h:222 [inline]
skb_expand_head+0x318/0x390 net/core/skbuff.c:2010
ip6_finish_output2+0x10f6/0x1530 net/ipv6/ip6_output.c:72
__ip6_finish_output net/ipv6/ip6_output.c:201 [inline]
ip6_finish_output+0x6a0/0xa80 net/ipv6/ip6_output.c:212
ip6tunnel_xmit include/net/ip6_tunnel.h:161 [inline]
udp_tunnel6_xmit_skb+0x587/0x9c0 net/ipv6/ip6_udp_tunnel.c:109
send6+0x6b7/0xac0 drivers/net/wireguard/socket.c:152
wg_socket_send_skb_to_peer+0x111/0x1d0 drivers/net/wireguard/socket.c:178
wg_packet_create_data_done drivers/net/wireguard/send.c:251 [inline]
wg_packet_tx_worker+0x1bb/0x810 drivers/net/wireguard/send.c:276
process_one_work+0x8a9/0x11d0 kernel/workqueue.c:2292
worker_thread+0xa47/0x1200 kernel/workqueue.c:2439
kthread+0x28d/0x320 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:308
</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 syzk...@googlegroups.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 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