[syzbot] [net?] WARNING in nsim_fib_event_nb

[syzbot <syzbot+a259a17220263c2d73fc@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    deeed351e982 Merge branch 'pds_core-cleanups'
git tree:       net-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1125e39b980000
kernel config:  https://syzkaller.appspot.com/x/.config?x=96ee122b7e5ad7d4
dashboard link: https://syzkaller.appspot.com/bug?extid=a259a17220263c2d73fc
compiler:       Debian clang version 20.1.2 (++20250402124445+58df0ef89dd6-1~exp1~20250402004600.97), Debian LLD 20.1.2
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=16a46f74580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15e2d02f980000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/f9cc381b3437/disk-deeed351.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2df0da84738b/vmlinux-deeed351.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a1f015928ca2/bzImage-deeed351.xz

The issue was bisected to:

commit e6f497955fb6a072999db491a01dd3a203d5bcea
Author: Kuniyuki Iwashima <kuniyu@amazon.com>
Date:   Fri Apr 18 00:03:45 2025 +0000

    ipv6: Check GATEWAY in rtm_to_fib6_multipath_config().

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=153481cc580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=173481cc580000
console output: https://syzkaller.appspot.com/x/log.txt?x=133481cc580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a259a17220263c2d73fc@syzkaller.appspotmail.com
Fixes: e6f497955fb6 ("ipv6: Check GATEWAY in rtm_to_fib6_multipath_config().")

IPv6: RTM_NEWROUTE with no NLM_F_CREATE or NLM_F_REPLACE
IPv6: NLM_F_CREATE should be set when creating new route
IPv6: NLM_F_CREATE should be set when creating new route
------------[ cut here ]------------
WARNING: CPU: 0 PID: 5822 at drivers/net/netdevsim/fib.c:831 nsim_fib6_event_init drivers/net/netdevsim/fib.c:831 [inline]
WARNING: CPU: 0 PID: 5822 at drivers/net/netdevsim/fib.c:831 nsim_fib6_prepare_event drivers/net/netdevsim/fib.c:947 [inline]
WARNING: CPU: 0 PID: 5822 at drivers/net/netdevsim/fib.c:831 nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:1003 [inline]
WARNING: CPU: 0 PID: 5822 at drivers/net/netdevsim/fib.c:831 nsim_fib_event_nb+0xed8/0x1080 drivers/net/netdevsim/fib.c:1043
Modules linked in:
CPU: 0 UID: 0 PID: 5822 Comm: syz-executor175 Not tainted 6.15.0-rc3-syzkaller-00644-gdeeed351e982 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
RIP: 0010:nsim_fib6_event_init drivers/net/netdevsim/fib.c:831 [inline]
RIP: 0010:nsim_fib6_prepare_event drivers/net/netdevsim/fib.c:947 [inline]
RIP: 0010:nsim_fib_event_schedule_work drivers/net/netdevsim/fib.c:1003 [inline]
RIP: 0010:nsim_fib_event_nb+0xed8/0x1080 drivers/net/netdevsim/fib.c:1043
Code: fa be 02 00 00 00 eb 0a e8 25 a2 bf fa be 01 00 00 00 4c 89 f7 e8 38 e6 b7 fd 4c 8b 64 24 08 e9 91 f4 ff ff e8 09 a2 bf fa 90 <0f> 0b 90 e9 70 fb ff ff 44 89 e9 80 e1 07 80 c1 03 38 c1 0f 8c 35
RSP: 0018:ffffc90003fff028 EFLAGS: 00010293
RAX: ffffffff87001b77 RBX: 0000000000000002 RCX: ffff88802d180000
RDX: 0000000000000000 RSI: 0000000000000002 RDI: 0000000000000001
RBP: dffffc0000000000 R08: ffff888078d6642f R09: 1ffff1100f1acc85
R10: dffffc0000000000 R11: ffffed100f1acc86 R12: ffff888072f34000
R13: ffffc90003fff1a0 R14: 0000000000000001 R15: ffffc90003fff1b8
FS:  00005555830fa380(0000) GS:ffff8881260c4000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007d7da000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 notifier_call_chain+0x1b3/0x3e0 kernel/notifier.c:85
 atomic_notifier_call_chain+0xda/0x180 kernel/notifier.c:223
 call_fib_notifiers+0x31/0x60 net/core/fib_notifier.c:35
 call_fib6_multipath_entry_notifiers+0xe6/0x150 net/ipv6/ip6_fib.c:427
 ip6_route_multipath_add net/ipv6/route.c:5593 [inline]
 inet6_rtm_newroute+0x1a0c/0x1c70 net/ipv6/route.c:5717
 rtnetlink_rcv_msg+0x7cc/0xb70 net/core/rtnetlink.c:6955
 netlink_rcv_skb+0x219/0x490 net/netlink/af_netlink.c:2534
 netlink_unicast_kernel net/netlink/af_netlink.c:1313 [inline]
 netlink_unicast+0x758/0x8d0 net/netlink/af_netlink.c:1339
 netlink_sendmsg+0x805/0xb30 net/netlink/af_netlink.c:1883
 sock_sendmsg_nosec net/socket.c:712 [inline]
 __sock_sendmsg+0x219/0x270 net/socket.c:727
 ____sys_sendmsg+0x505/0x830 net/socket.c:2566
 ___sys_sendmsg+0x21f/0x2a0 net/socket.c:2620
 __sys_sendmsg net/socket.c:2652 [inline]
 __do_sys_sendmsg net/socket.c:2657 [inline]
 __se_sys_sendmsg net/socket.c:2655 [inline]
 __x64_sys_sendmsg+0x19b/0x260 net/socket.c:2655
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6d91f8d999
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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff05e7f5e8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000200000000300 RCX: 00007f6d91f8d999
RDX: 0000000000000000 RSI: 0000200000000100 RDI: 0000000000000003
RBP: 0000000000000000 R08: 0000555500000000 R09: 0000555500000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>


---
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