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BUG: KCSAN: data-race in pfkey_is_alive / pfkey_register

read to 0xffff888121c3e2f8 of 4 bytes by task 16385 on cpu 0:
 pfkey_is_alive+0xb5/0x130 net/key/af_key.c:3122
 km_is_alive net/xfrm/xfrm_state.c:2254 [inline]
 xfrm_state_find+0x1273/0x27c0 net/xfrm/xfrm_state.c:1109
 xfrm_tmpl_resolve_one net/xfrm/xfrm_policy.c:2391 [inline]
 xfrm_tmpl_resolve+0x21e/0x890 net/xfrm/xfrm_policy.c:2436
 xfrm_resolve_and_create_bundle+0x9d/0x12d0 net/xfrm/xfrm_policy.c:2727
 xfrm_lookup_with_ifid+0x1b7/0x1310 net/xfrm/xfrm_policy.c:3050
 xfrm_lookup net/xfrm/xfrm_policy.c:3174 [inline]
 xfrm_lookup_route+0x44/0x100 net/xfrm/xfrm_policy.c:3185
 ip_route_output_flow+0x9d/0xb0 net/ipv4/route.c:2726
 udp_sendmsg+0x1376/0x1900 net/ipv4/udp.c:1144
 udpv6_sendmsg+0xd97/0x1c20 net/ipv6/udp.c:1284
 inet6_sendmsg+0x6d/0x90 net/ipv6/af_inet6.c:576
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311
 __sys_sendmmsg+0x123/0x350 net/socket.c:2413
 __do_sys_sendmmsg net/socket.c:2442 [inline]
 __se_sys_sendmmsg net/socket.c:2439 [inline]
 __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888121c3e2f8 of 4 bytes by task 16389 on cpu 1:
 pfkey_register+0xb2/0x500 net/key/af_key.c:1701
 pfkey_process+0x429/0x4a0 net/key/af_key.c:2834
 pfkey_sendmsg+0x2a4/0x520 net/key/af_key.c:3673
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 ___sys_sendmsg+0x59d/0x5d0 net/socket.c:2311
 __sys_sendmsg+0xa0/0x160 net/socket.c:2356
 __do_sys_sendmsg net/socket.c:2365 [inline]
 __se_sys_sendmsg net/socket.c:2363 [inline]
 __x64_sys_sendmsg+0x51/0x70 net/socket.c:2363
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16389 Comm: syz-executor.1 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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