------------[ cut here ]------------
socket already in reuseport group
WARNING: CPU: 0 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: 0 PID: 3496 Comm: syzkaller869503 Not tainted 4.15.0-rc6+ #245
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:1079
RIP: 0010:reuseport_add_sock+0x742/0x9b0 net/core/sock_reuseport.c:117
RSP: 0018:ffff8801bf5f7968 EFLAGS: 00010286
RAX: dffffc0000000008 RBX: ffff8801bf4905c0 RCX: ffffffff8159d9de
RDX: 0000000000000000 RSI: 1ffff10037ebeee8 RDI: 0000000000000293
RBP: ffff8801bf5f7b00 R08: 1ffff10037ebeeaa R09: 0000000000000000
R10: ffff8801bf5f7820 R11: 0000000000000000 R12: 1ffff10037ebef37
R13: ffff8801bf47b930 R14: ffff8801bf5f7ad8 R15: 1ffff10037ebef3b
 inet_reuseport_add_sock net/ipv4/inet_hashtables.c:456 [inline]
 __inet_hash+0x767/0xb90 net/ipv4/inet_hashtables.c:477
 inet_hash+0x61/0x90 net/ipv4/inet_hashtables.c:501
 inet_csk_listen_start+0x38f/0x460 net/ipv4/inet_connection_sock.c:885
 inet_listen+0x19a/0x440 net/ipv4/af_inet.c:228
 SYSC_listen net/socket.c:1483 [inline]
 SyS_listen+0x1aa/0x350 net/socket.c:1469
 entry_SYSCALL_64_fastpath+0x23/0x9a
RIP: 0033:0x445639
RSP: 002b:00007f2966197db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000032
RAX: ffffffffffffffda RBX: 00000000006dac24 RCX: 0000000000445639
RDX: 0000000000445639 RSI: 0000000000000000 RDI: 0000000000000006
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc328a273f R14: 00007f29661989c0 R15: 0000000000000008
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..