sock: process `syz-executor4' is using obsolete setsockopt SO_BSDCOMPAT

=============================
WARNING: suspicious RCU usage
4.15.0-rc8+ #195 Not tainted
-----------------------------
./include/net/inet_sock.h:136 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor4/400:
 #0:  (sk_lock-AF_INET6){+.+.}, at: [<0000000039318892>] lock_sock include/net/sock.h:1463 [inline]
 #0:  (sk_lock-AF_INET6){+.+.}, at: [<0000000039318892>] sock_setsockopt+0x16b/0x1af0 net/core/sock.c:717

stack backtrace:
CPU: 1 PID: 400 Comm: syz-executor4 Not tainted 4.15.0-rc8+ #195
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
 lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
 ireq_opt_deref include/net/inet_sock.h:135 [inline]
 inet_csk_route_req+0x824/0xca0 net/ipv4/inet_connection_sock.c:544
 dccp_v4_send_response+0xa7/0x650 net/dccp/ipv4.c:485
 dccp_v4_conn_request+0x9ee/0x11b0 net/dccp/ipv4.c:633
 dccp_v6_conn_request+0xd30/0x1350 net/dccp/ipv6.c:317
 dccp_rcv_state_process+0x574/0x1620 net/dccp/input.c:612
 dccp_v4_do_rcv+0xf1/0x160 net/dccp/ipv4.c:682
 dccp_v6_do_rcv+0x823/0x9c0 net/dccp/ipv6.c:578
 sk_backlog_rcv include/net/sock.h:908 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2274
 release_sock+0xa4/0x2a0 net/core/sock.c:2789
 sock_setsockopt+0x528/0x1af0 net/core/sock.c:1068
 SYSC_setsockopt net/socket.c:1819 [inline]
 SyS_setsockopt+0x2ff/0x360 net/socket.c:1802
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e39
RSP: 002b:00007fa319d35c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e39
RDX: 000000000000000e RSI: 0000000000000001 RDI: 0000000000000013
RBP: 00000000000003a4 R08: 0000000000000004 R09: 0000000000000000
R10: 00000000208ab000 R11: 0000000000000212 R12: 00000000006f3800
R13: 00000000ffffffff R14: 00007fa319d366d4 R15: 0000000000000000

=============================
WARNING: suspicious RCU usage
4.15.0-rc8+ #195 Not tainted
-----------------------------
./include/net/inet_sock.h:136 suspicious rcu_dereference_check() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syz-executor4/400:
 #0:  (sk_lock-AF_INET6){+.+.}, at: [<0000000039318892>] lock_sock include/net/sock.h:1463 [inline]
 #0:  (sk_lock-AF_INET6){+.+.}, at: [<0000000039318892>] sock_setsockopt+0x16b/0x1af0 net/core/sock.c:717

stack backtrace:
CPU: 1 PID: 400 Comm: syz-executor4 Not tainted 4.15.0-rc8+ #195
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
 lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
 ireq_opt_deref include/net/inet_sock.h:135 [inline]
 dccp_v4_send_response+0x4b6/0x650 net/dccp/ipv4.c:496
 dccp_v4_conn_request+0x9ee/0x11b0 net/dccp/ipv4.c:633
 dccp_v6_conn_request+0xd30/0x1350 net/dccp/ipv6.c:317
 dccp_rcv_state_process+0x574/0x1620 net/dccp/input.c:612
 dccp_v4_do_rcv+0xf1/0x160 net/dccp/ipv4.c:682
 dccp_v6_do_rcv+0x823/0x9c0 net/dccp/ipv6.c:578
 sk_backlog_rcv include/net/sock.h:908 [inline]
 __release_sock+0x124/0x360 net/core/sock.c:2274
 release_sock+0xa4/0x2a0 net/core/sock.c:2789
 sock_setsockopt+0x528/0x1af0 net/core/sock.c:1068
 SYSC_setsockopt net/socket.c:1819 [inline]
 SyS_setsockopt+0x2ff/0x360 net/socket.c:1802
 entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x452e39
RSP: 002b:00007fa319d35c58 EFLAGS: 00000212 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000452e39
RDX: 000000000000000e RSI: 0000000000000001 RDI: 0000000000000013
RBP: 00000000000003a4 R08: 0000000000000004 R09: 0000000000000000
R10: 00000000208ab000 R11: 0000000000000212 R12: 00000000006f3800
R13: 00000000ffffffff R14: 00007fa319d366d4 R15: 0000000000000000