------------[ cut here ]------------
socket already in reuseport group
WARNING: CPU: 1 PID: 3496 at net/core/sock_reuseport.c:119 reuseport_add_sock+0x742/0x9b0 net/core/sock_reuseport.c:117
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 3496 Comm: syzkaller959078 Not tainted 4.15.0-rc5+ #171
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x257 lib/dump_stack.c:53
 panic+0x1e4/0x41c kernel/panic.c:183
 __warn+0x1dc/0x200 kernel/panic.c:547
 report_bug+0x211/0x2d0 lib/bug.c:184
 fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
 fixup_bug arch/x86/kernel/traps.c:247 [inline]
 do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
 do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
 invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1061
RIP: 0010:reuseport_add_sock+0x742/0x9b0 net/core/sock_reuseport.c:117
RSP: 0018:ffff8801c09e7918 EFLAGS: 00010282
RAX: dffffc0000000008 RBX: ffff8801c08fb140 RCX: ffffffff8159ce7e
RDX: 0000000000000000 RSI: 1ffff1003813cede RDI: 0000000000000293
RBP: ffff8801c09e7ab0 R08: 1ffff1003813cea0 R09: 0000000000000000
R10: ffff8801c09e77d0 R11: 0000000000000000 R12: 1ffff1003813cf2d
R13: ffff8801c091d930 R14: ffff8801c09e7a88 R15: 1ffff1003813cf31
 inet_reuseport_add_sock net/ipv4/inet_hashtables.c:570 [inline]
 __inet_hash+0x9c4/0x10d0 net/ipv4/inet_hashtables.c:591
 inet_hash+0x61/0x90 net/ipv4/inet_hashtables.c:617
 inet_csk_listen_start+0x258/0x310 net/ipv4/inet_connection_sock.c:885
 inet_listen+0x19a/0x440 net/ipv4/af_inet.c:229
 SYSC_listen net/socket.c:1475 [inline]
 SyS_listen+0x1aa/0x350 net/socket.c:1461
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x445639
RSP: 002b:00007f301e183db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 0000000000445639
RDX: 0000000000445639 RSI: 0000000000000000 RDI: 0000000000000005
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd7185c9ef R14: 00007f301e1849c0 R15: 0000000000000008
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..