netdev - [syzbot] [net?] WARNING in rt6_multipath

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Message-ID: <68135815.050a0220.3a872c.0010.GAE@google.com>
Date: Thu, 01 May 2025 04:16:37 -0700
From: syzbot <syzbot+d842f24c4e2bae159341@...kaller.appspotmail.com>
To: davem@...emloft.net, dsahern@...nel.org, edumazet@...gle.com, 
	horms@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org, 
	netdev@...r.kernel.org, pabeni@...hat.com, syzkaller-bugs@...glegroups.com
Subject: [syzbot] [net?] WARNING in rt6_multipath_rebalance (2)

Hello,

syzbot found the following issue on:

HEAD commit:    cc17b4b9c332 Merge branch 'io_uring-zcrx-fix-selftests-and..
git tree:       net-next
console output: https://syzkaller.appspot.com/x/log.txt?x=125b8374580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7e367ce4a19f69ba
dashboard link: https://syzkaller.appspot.com/bug?extid=d842f24c4e2bae159341
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/0e09cf367bdd/disk-cc17b4b9.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4ab63344d74c/vmlinux-cc17b4b9.xz
kernel image: https://storage.googleapis.com/syzbot-assets/14915e0e32b3/bzImage-cc17b4b9.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d842f24c4e2bae159341@...kaller.appspotmail.com

batman_adv: batadv0: Removing interface: batadv_slave_1
veth1_macvtap: left promiscuous mode
veth0_macvtap: left promiscuous mode
veth1_vlan: left promiscuous mode
veth0_vlan: left promiscuous mode
------------[ cut here ]------------
WARNING: CPU: 0 PID: 36 at net/ipv6/route.c:4822 rt6_multipath_rebalance+0x455/0x8b0 net/ipv6/route.c:4822
Modules linked in:
CPU: 0 UID: 0 PID: 36 Comm: kworker/u8:2 Not tainted 6.15.0-rc3-syzkaller-00584-gcc17b4b9c332 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: netns cleanup_net
RIP: 0010:rt6_multipath_rebalance+0x455/0x8b0 net/ipv6/route.c:4822
Code: ff ff 44 89 e1 80 e1 07 38 c1 0f 8c 85 fe ff ff 4c 89 e7 e8 2d a0 13 f8 e9 78 fe ff ff e8 e3 aa b1 f7 eb 05 e8 dc aa b1 f7 90 <0f> 0b 90 48 83 c4 10 5b 41 5c 41 5d 41 5e 41 5f 5d c3 cc cc cc cc
RSP: 0018:ffffc90000ad6ee0 EFLAGS: 00010293
RAX: ffffffff8a0e129d RBX: ffff88802f515000 RCX: ffff8881412d9e00
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000
RBP: dffffc0000000000 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff5200015add4 R12: ffff88802f5150de
R13: ffff88802f515090 R14: 0000000000000000 R15: 1ffff11005ea2a12
FS:  0000000000000000(0000) GS:ffff8881260c4000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f94077eeb68 CR3: 000000000dd36000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 fib6_ifdown+0x401/0x4c0 net/ipv6/route.c:4942
 fib6_clean_node+0x24a/0x590 net/ipv6/ip6_fib.c:2249
 fib6_walk_continue+0x678/0x910 net/ipv6/ip6_fib.c:2174
 fib6_walk+0x149/0x290 net/ipv6/ip6_fib.c:2222
 fib6_clean_tree net/ipv6/ip6_fib.c:2302 [inline]
 __fib6_clean_all+0x234/0x380 net/ipv6/ip6_fib.c:2318
 rt6_sync_down_dev net/ipv6/route.c:4970 [inline]
 rt6_disable_ip+0x120/0x720 net/ipv6/route.c:4975
 addrconf_ifdown+0x15d/0x1880 net/ipv6/addrconf.c:3854
 addrconf_notify+0x1bc/0x1010 net/ipv6/addrconf.c:-1
 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
 call_netdevice_notifiers_extack net/core/dev.c:2266 [inline]
 call_netdevice_notifiers net/core/dev.c:2280 [inline]
 dev_close_many+0x29c/0x410 net/core/dev.c:1783
 unregister_netdevice_many_notify+0x834/0x2320 net/core/dev.c:12006
 unregister_netdevice_many net/core/dev.c:12099 [inline]
 default_device_exit_batch+0x819/0x890 net/core/dev.c:12601
 ops_exit_list net/core/net_namespace.c:206 [inline]
 ops_undo_list+0x522/0x990 net/core/net_namespace.c:253
 cleanup_net+0x4c5/0x8a0 net/core/net_namespace.c:686
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0xadb/0x17a0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x70e/0x8a0 kernel/kthread.c:464
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>


---
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