[v6.1] WARNING in rt6_multipath_rebalance

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7e69c33e4858 Linux 6.1.142
git tree: linux-6.1.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13784582580000
kernel config: https://syzkaller.appspot.com/x/.config?x=51337ef9bf75e4a2
dashboard link: https://syzkaller.appspot.com/bug?extid=78db9e9e70426856f776
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a7b7ddd6febc/disk-7e69c33e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/93da2e0ed397/vmlinux-7e69c33e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e19124af9a1c/bzImage-7e69c33e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+78db9e...@syzkaller.appspotmail.com

------------[ cut here ]------------
WARNING: CPU: 0 PID: 4426 at net/ipv6/route.c:4796 rt6_multipath_first_sibling net/ipv6/route.c:4718 [inline]
WARNING: CPU: 0 PID: 4426 at net/ipv6/route.c:4796 rt6_multipath_rebalance+0x449/0x8a0 net/ipv6/route.c:4795
Modules linked in:
CPU: 0 PID: 4426 Comm: kworker/u4:13 Not tainted 6.1.142-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: netns cleanup_net
RIP: 0010:rt6_multipath_rebalance+0x449/0x8a0 net/ipv6/route.c:4796
Code: e8 fc 80 f1 f8 e9 1c fe ff ff 44 89 e1 80 e1 07 38 c1 0f 8c 85 fe ff ff 4c 89 e7 e8 c1 80 f1 f8 e9 78 fe ff ff e8 37 05 a0 f8 <0f> 0b eb 07 e8 2e 05 a0 f8 0f 0b 48 83 c4 10 5b 41 5c 41 5d 41 5e
RSP: 0018:ffffc90004877120 EFLAGS: 00010293
RAX: ffffffff88e0d249 RBX: ffff8880584da800 RCX: ffff888019eb3b80
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: dffffc0000000000 R09: ffffed100f6bcc42
R10: ffffed100f6bcc42 R11: 1ffff1100f6bcc41 R12: ffff8880584da8be
R13: ffff8880584da880 R14: 0000000000000000 R15: 1ffff1100b09b510
FS: 0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb344d0a000 CR3: 000000005c293000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
fib6_ifdown+0x3ef/0x4a0 net/ipv6/route.c:4916
fib6_clean_node+0x244/0x580 net/ipv6/ip6_fib.c:2191
fib6_walk_continue+0x640/0x8c0 net/ipv6/ip6_fib.c:2116
fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2164
fib6_clean_tree net/ipv6/ip6_fib.c:2244 [inline]
__fib6_clean_all+0x231/0x370 net/ipv6/ip6_fib.c:2260
rt6_sync_down_dev net/ipv6/route.c:4944 [inline]
rt6_disable_ip+0x120/0x7f0 net/ipv6/route.c:4949
addrconf_ifdown+0x162/0x1a10 net/ipv6/addrconf.c:3804
addrconf_notify+0x405/0xf40 net/ipv6/addrconf.c:-1
notifier_call_chain kernel/notifier.c:87 [inline]
raw_notifier_call_chain+0xcb/0x160 kernel/notifier.c:455
call_netdevice_notifiers_extack net/core/dev.c:2039 [inline]
call_netdevice_notifiers net/core/dev.c:2053 [inline]
dev_close_many+0x28d/0x400 net/core/dev.c:1601
unregister_netdevice_many+0x471/0x1840 net/core/dev.c:10952
sit_exit_batch_net+0x498/0x4e0 net/ipv6/sit.c:1887
ops_exit_list net/core/net_namespace.c:177 [inline]
cleanup_net+0x77b/0xb80 net/core/net_namespace.c:640
process_one_work+0x898/0x1160 kernel/workqueue.c:2292
worker_thread+0xaa2/0x1250 kernel/workqueue.c:2439
kthread+0x29d/0x330 kernel/kthread.c:376
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
</TASK>


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.