WARNING in fib6_add

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 893af1c7 Linux 4.19.66
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=10428672600000
kernel config: https://syzkaller.appspot.com/x/.config?x=d5fac5a8617b8643
dashboard link: https://syzkaller.appspot.com/bug?extid=77b188fc64591bd79b68
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

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

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+77b188...@syzkaller.appspotmail.com

IPv6: NLM_F_REPLACE set, but no existing node found!
------------[ cut here ]------------
WARNING: CPU: 0 PID: 28001 at net/ipv6/ip6_fib.c:1352
fib6_add.cold+0x11/0xdc net/ipv6/ip6_fib.c:1352
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 28001 Comm: syz-executor.3 Not tainted 4.19.66 #40
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
panic+0x263/0x507 kernel/panic.c:185
__warn.cold+0x20/0x4a kernel/panic.c:540
report_bug+0x263/0x2b0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
fixup_bug arch/x86/kernel/traps.c:173 [inline]
do_error_trap+0x204/0x360 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:1037
RIP: 0010:fib6_add.cold+0x11/0xdc net/ipv6/ip6_fib.c:1352
Code: 8f ff ff e8 0a 79 6a fb 48 c7 c7 c0 18 ea 87 e8 72 e0 54 fb e9 8c 94
ff ff e8 f4 78 6a fb 48 c7 c7 20 13 ea 87 e8 5c e0 54 fb <0f> 0b 48 8b 95
40 ff ff ff b8 ff ff 37 00 48 c1 e0 2a 48 c1 ea 03
RSP: 0018:ffff888063307418 EFLAGS: 00010282
RAX: 0000000000000024 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffffff8155d916 RDI: ffffed100c660e75
RBP: ffff888063307568 R08: 0000000000000024 R09: ffff88808207c988
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880939aeea0
R13: ffff8880a04e7300 R14: 0000000000000000 R15: ffff8880939aee80
__ip6_ins_rt+0x54/0x80 net/ipv6/route.c:1164
ip6_route_add+0x5a/0xd0 net/ipv6/route.c:3210
inet6_rtm_newroute+0x139/0x150 net/ipv6/route.c:4604
rtnetlink_rcv_msg+0x463/0xb00 net/core/rtnetlink.c:4747
netlink_rcv_skb+0x17d/0x460 net/netlink/af_netlink.c:2454
rtnetlink_rcv+0x1d/0x30 net/core/rtnetlink.c:4765
netlink_unicast_kernel net/netlink/af_netlink.c:1317 [inline]
netlink_unicast+0x537/0x720 net/netlink/af_netlink.c:1343
netlink_sendmsg+0x8ae/0xd70 net/netlink/af_netlink.c:1908
sock_sendmsg_nosec net/socket.c:622 [inline]
sock_sendmsg+0xd7/0x130 net/socket.c:632
___sys_sendmsg+0x803/0x920 net/socket.c:2115
__sys_sendmsg+0x105/0x1d0 net/socket.c:2153
__do_sys_sendmsg net/socket.c:2162 [inline]
__se_sys_sendmsg net/socket.c:2160 [inline]
__x64_sys_sendmsg+0x78/0xb0 net/socket.c:2160
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: fd b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b7 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f344072bc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000020000380 RDI: 0000000000000003
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f344072c6d4
R13: 00000000004c7082 R14: 00000000004dc6a8 R15: 00000000ffffffff
Kernel Offset: disabled
Rebooting in 86400 seconds..


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[syzbot]

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