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BUG: KCSAN: data-race in xfrm_policy_insert / xfrm_policy_insert

read to 0xffffffff86fd5790 of 4 bytes by task 21052 on cpu 1:
 xfrm_policy_insert+0x308/0x820
 xfrm_add_policy+0x183/0x430 net/xfrm/xfrm_user.c:1982
 xfrm_user_rcv_msg+0x3c7/0x4e0 net/xfrm/xfrm_user.c:3150
 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2546
 xfrm_netlink_rcv+0x47/0x60 net/xfrm/xfrm_user.c:3172
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1913
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg net/socket.c:747 [inline]
 ____sys_sendmsg+0x375/0x4c0 net/socket.c:2503
 ___sys_sendmsg net/socket.c:2557 [inline]
 __sys_sendmsg+0x1e3/0x270 net/socket.c:2586
 __do_sys_sendmsg net/socket.c:2595 [inline]
 __se_sys_sendmsg net/socket.c:2593 [inline]
 __x64_sys_sendmsg+0x46/0x50 net/socket.c:2593
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

write to 0xffffffff86fd5790 of 4 bytes by task 21050 on cpu 0:
 xfrm_gen_index net/xfrm/xfrm_policy.c:1385 [inline]
 xfrm_policy_insert+0x343/0x820 net/xfrm/xfrm_policy.c:1606
 xfrm_add_policy+0x183/0x430 net/xfrm/xfrm_user.c:1982
 xfrm_user_rcv_msg+0x3c7/0x4e0 net/xfrm/xfrm_user.c:3150
 netlink_rcv_skb+0x126/0x220 net/netlink/af_netlink.c:2546
 xfrm_netlink_rcv+0x47/0x60 net/xfrm/xfrm_user.c:3172
 netlink_unicast_kernel net/netlink/af_netlink.c:1339 [inline]
 netlink_unicast+0x56f/0x640 net/netlink/af_netlink.c:1365
 netlink_sendmsg+0x665/0x770 net/netlink/af_netlink.c:1913
 sock_sendmsg_nosec net/socket.c:724 [inline]
 sock_sendmsg net/socket.c:747 [inline]
 ____sys_sendmsg+0x375/0x4c0 net/socket.c:2503
 ___sys_sendmsg net/socket.c:2557 [inline]
 __sys_sendmsg+0x1e3/0x270 net/socket.c:2586
 __do_sys_sendmsg net/socket.c:2595 [inline]
 __se_sys_sendmsg net/socket.c:2593 [inline]
 __x64_sys_sendmsg+0x46/0x50 net/socket.c:2593
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000ba70 -> 0x0000ba78

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21050 Comm: syz-executor.4 Not tainted 6.4.0-rc7-syzkaller-00014-g692b7dc87ca6 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/27/2023
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