TCP: request_sock_TCPv6: Possible SYN flooding on port 20006. Sending cookies. Check SNMP counters. BUG: using __this_cpu_add() in preemptible [00000000] code: syz-executor2/10864 caller is __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62 CPU: 1 PID: 10864 Comm: syz-executor2 Not tainted 4.4.113-g962d1f3 #2 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 0000000000000000 12164e00ceafffde ffff8800b24cf800 ffffffff81d028ed 0000000000000001 ffffffff839fe3a0 ffffffff83cef6a0 ffff8800b40b0000 0000000000000003 ffff8800b24cf840 ffffffff81d62834 ffffffff810002b8 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x124 lib/dump_stack.c:51 [] check_preemption_disabled+0x1d4/0x200 lib/smp_processor_id.c:46 [] ? 0xffffffff810002b8 [] __this_cpu_preempt_check+0x1c/0x20 lib/smp_processor_id.c:62 [] tcp_try_coalesce+0x249/0x4d0 net/ipv4/tcp_input.c:4278 [] tcp_queue_rcv+0x127/0x720 net/ipv4/tcp_input.c:4485 [] tcp_send_rcvq+0x39b/0x450 net/ipv4/tcp_input.c:4531 [] tcp_sendmsg+0x1e8f/0x2b10 net/ipv4/tcp.c:1134 [] inet_sendmsg+0x2bc/0x4c0 net/ipv4/af_inet.c:755 [] sock_sendmsg_nosec net/socket.c:625 [inline] [] sock_sendmsg+0xca/0x110 net/socket.c:635 [] SYSC_sendto+0x2c8/0x340 net/socket.c:1665 [] SyS_sendto+0x40/0x50 net/socket.c:1633 [] entry_SYSCALL_64_fastpath+0x1c/0x98