syzbot

kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Dumping ftrace buffer:
   (ftrace buffer empty)
Modules linked in:
CPU: 0 PID: 3197 Comm: syzkaller627078 Not tainted 4.15.0-rc5+ #241
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:fib6_add+0x736/0x15a0 net/ipv6/ip6_fib.c:1244
RSP: 0018:ffff8801c773ec00 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000020 RCX: ffffffff84794465
RDX: 0000000000000004 RSI: ffff8801c7715530 RDI: 0000000000000282
RBP: ffff8801c773ef30 R08: 1ffff10038ee7c67 R09: 0000000000000000
R10: ffff8801c773edf8 R11: 0000000000000000 R12: 00000000fffffffe
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000009
FS:  00000000009a5880(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000204db000 CR3: 00000001c8cc1001 CR4: 00000000001606f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __ip6_ins_rt+0x6c/0x90 net/ipv6/route.c:1006
 ip6_route_multipath_add+0xd14/0x16c0 net/ipv6/route.c:3833
 inet6_rtm_newroute+0xdc/0x160 net/ipv6/route.c:3957
 rtnetlink_rcv_msg+0x733/0x1020 net/core/rtnetlink.c:4411
 netlink_rcv_skb+0x21e/0x460 net/netlink/af_netlink.c:2408
 rtnetlink_rcv+0x1c/0x20 net/core/rtnetlink.c:4423
 netlink_unicast_kernel net/netlink/af_netlink.c:1275 [inline]
 netlink_unicast+0x4e8/0x6f0 net/netlink/af_netlink.c:1301
 netlink_sendmsg+0xa4a/0xe60 net/netlink/af_netlink.c:1864
 sock_sendmsg_nosec net/socket.c:636 [inline]
 sock_sendmsg+0xca/0x110 net/socket.c:646
 sock_write_iter+0x31a/0x5d0 net/socket.c:915
 call_write_iter include/linux/fs.h:1772 [inline]
 do_iter_readv_writev+0x525/0x7f0 fs/read_write.c:653
 do_iter_write+0x154/0x540 fs/read_write.c:932
 vfs_writev+0x18a/0x340 fs/read_write.c:977
 do_writev+0xfc/0x2a0 fs/read_write.c:1012
 SYSC_writev fs/read_write.c:1085 [inline]
 SyS_writev+0x27/0x30 fs/read_write.c:1082
 entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x43fcd9
RSP: 002b:00007ffc778b2438 EFLAGS: 00000203 ORIG_RAX: 0000000000000014
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 000000000043fcd9
RDX: 0000000000000001 RSI: 00000000200c1000 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000203 R12: 0000000000401640
R13: 00000000004016d0 R14: 0000000000000000 R15: 0000000000000000
Code: f1 a9 f6 fc e8 2c f2 e2 fc 85 c0 0f 85 d5 03 00 00 49 8d 5e 20 e8 db a9 f6 fc 48 89 da 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 <80> 3c 02 00 0f 85 5a 0c 00 00 4d 39 ee 4d 8b 7e 20 0f 95 c0 4c 
RIP: fib6_add+0x736/0x15a0 net/ipv6/ip6_fib.c:1244 RSP: ffff8801c773ec00
---[ end trace 6ae18838beccf3fa ]---