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BUG: KCSAN: data-race in ip_tunnel_xmit / ip_tunnel_xmit

write to 0xffff88812a5b3170 of 8 bytes by task 20810 on cpu 1:
 ip_tunnel_xmit+0x7a6/0x11c0 net/ipv4/ip_tunnel.c:756
 sit_tunnel_xmit__ net/ipv6/sit.c:1058 [inline]
 sit_tunnel_xmit+0x3c2/0x11f0 net/ipv6/sit.c:1074
 __netdev_start_xmit include/linux/netdevice.h:4944 [inline]
 netdev_start_xmit include/linux/netdevice.h:4958 [inline]
 xmit_one+0xf9/0x270 net/core/dev.c:3654
 dev_hard_start_xmit net/core/dev.c:3670 [inline]
 __dev_queue_xmit+0xd44/0x1300 net/core/dev.c:4245
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4278
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1524
 neigh_output include/net/neighbour.h:510 [inline]
 ip_finish_output2+0x874/0xb10 net/ipv4/ip_output.c:230
 __ip_finish_output net/ipv4/ip_output.c:252 [inline]
 ip_finish_output+0x2fa/0x490 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:448 [inline]
 ip_local_out+0x167/0x230 net/ipv4/ip_output.c:126
 ip_send_skb+0x27/0x90 net/ipv4/ip_output.c:1568
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:953
 udp_sendmsg+0xfe4/0x12f0 net/ipv4/udp.c:1240
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:821
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812a5b3170 of 8 bytes by task 20821 on cpu 0:
 ip_tunnel_xmit+0x794/0x11c0 net/ipv4/ip_tunnel.c:756
 sit_tunnel_xmit__ net/ipv6/sit.c:1058 [inline]
 sit_tunnel_xmit+0x3c2/0x11f0 net/ipv6/sit.c:1074
 __netdev_start_xmit include/linux/netdevice.h:4944 [inline]
 netdev_start_xmit include/linux/netdevice.h:4958 [inline]
 xmit_one+0xf9/0x270 net/core/dev.c:3654
 dev_hard_start_xmit net/core/dev.c:3670 [inline]
 __dev_queue_xmit+0xd44/0x1300 net/core/dev.c:4245
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4278
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1524
 neigh_output include/net/neighbour.h:510 [inline]
 ip_finish_output2+0x874/0xb10 net/ipv4/ip_output.c:230
 __ip_finish_output net/ipv4/ip_output.c:252 [inline]
 ip_finish_output+0x2fa/0x490 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:448 [inline]
 ip_local_out+0x167/0x230 net/ipv4/ip_output.c:126
 ip_send_skb+0x27/0x90 net/ipv4/ip_output.c:1568
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:953
 udp_sendmsg+0xfe4/0x12f0 net/ipv4/udp.c:1240
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:821
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 20821 Comm: syz-executor.2 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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