[syzbot ci] Re: ipv6: Protect multiple routes insertion by table lock.

[syzbot ci]

syzbot ci has tested the following series

[v1] ipv6: Protect multiple routes insertion by table lock.
https://lore.kernel.org/all/20261023191517....@google.com
* [PATCH v1 net] ipv6: Protect multiple routes insertion by table lock.

and found the following issue:
WARNING: suspicious RCU usage in rt6_multipath_rebalance

Full report is available here:
https://ci.syzbot.org/series/7d878fa2-f84a-4468-85e2-c2a5e263aeff

***

WARNING: suspicious RCU usage in rt6_multipath_rebalance

tree: net
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/netdev/net.git
base: 7076f684d5132e6a6145e1da2fa74771ecd052e5
arch: amd64
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
config: https://ci.syzbot.org/builds/bbb3053f-f23f-4fe3-a9e9-85396428119d/config

IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
IPv6: NLM_F_CREATE should be set when creating new route
=============================
WARNING: suspicious RCU usage
syzkaller #0 Not tainted
-----------------------------
./include/net/addrconf.h:351 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
locks held by syz.2.3386/18922: 1, last CPU#0:
#0: ffff888177df3430 (&tb->tb6_lock){+...}-{3:3}, at: inet6_rtm_newroute+0x3dc/0x1ab0

stack backtrace:
CPU: 0 UID: 0 PID: 18922 Comm: syz.2.3386 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150
lockdep_rcu_suspicious+0x140/0x1d0
rt6_multipath_rebalance+0xf11/0x1080
fib6_del+0xada/0x15a0
inet6_rtm_newroute+0x15b5/0x1ab0
rtnetlink_rcv_msg+0x802/0xc00
netlink_rcv_skb+0x226/0x4a0
netlink_unicast+0x8ef/0xa80
netlink_sendmsg+0x7f0/0xb20
sock_sendmsg_nosec+0x14e/0x190
____sys_sendmsg+0x54e/0x850
___sys_sendmsg+0x2a5/0x360
__sys_sendmmsg+0x273/0x4e0
__x64_sys_sendmmsg+0xa0/0xc0
do_syscall_64+0x166/0x520
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa77459f559
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fa775488028 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fa774826090 RCX: 00007fa77459f559
RDX: 040000000000009f RSI: 00002000000002c0 RDI: 000000000000000b
RBP: 00007fa774636b20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fa774826128 R14: 00007fa774826090 R15: 00007fffd26b46d8
</TASK>


***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syz...@syzkaller.appspotmail.com

---
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