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BUG: KCSAN: data-race in ip_tunnel_xmit / ip_tunnel_xmit

write to 0xffff8881352f6170 of 8 bytes by task 16492 on cpu 0:
 ip_tunnel_xmit+0x907/0x11a0 net/ipv4/ip_tunnel.c:762
 sit_tunnel_xmit__ net/ipv6/sit.c:1065 [inline]
 sit_tunnel_xmit+0x3c2/0x11f0 net/ipv6/sit.c:1081
 __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:3659
 dev_hard_start_xmit net/core/dev.c:3675 [inline]
 __dev_queue_xmit+0x693/0xa50 net/core/dev.c:4285
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4318
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1525
 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:296 [inline]
 ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:448 [inline]
 ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
 ip_send_skb+0x27/0x90 net/ipv4/ip_output.c:1572
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:966
 udp_sendmsg+0xfe4/0x12f0 net/ipv4/udp.c:1253
 udpv6_sendmsg+0x520/0x16b0 net/ipv6/udp.c:1364
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:642
 sock_sendmsg_nosec net/socket.c:703 [inline]
 sock_sendmsg net/socket.c:723 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392
 ___sys_sendmsg net/socket.c:2446 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2532
 __do_sys_sendmmsg net/socket.c:2561 [inline]
 __se_sys_sendmmsg net/socket.c:2558 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2558
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881352f6170 of 8 bytes by task 16508 on cpu 1:
 ip_tunnel_xmit+0x8f5/0x11a0 net/ipv4/ip_tunnel.c:762
 sit_tunnel_xmit__ net/ipv6/sit.c:1065 [inline]
 sit_tunnel_xmit+0x3c2/0x11f0 net/ipv6/sit.c:1081
 __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:3659
 dev_hard_start_xmit net/core/dev.c:3675 [inline]
 __dev_queue_xmit+0x693/0xa50 net/core/dev.c:4285
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4318
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1525
 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:296 [inline]
 ip_output+0xf3/0x1a0 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:448 [inline]
 ip_local_out+0x164/0x220 net/ipv4/ip_output.c:126
 ip_send_skb+0x27/0x90 net/ipv4/ip_output.c:1572
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:966
 udp_sendmsg+0xfe4/0x12f0 net/ipv4/udp.c:1253
 udpv6_sendmsg+0x520/0x16b0 net/ipv6/udp.c:1364
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:642
 sock_sendmsg_nosec net/socket.c:703 [inline]
 sock_sendmsg net/socket.c:723 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2392
 ___sys_sendmsg net/socket.c:2446 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2532
 __do_sys_sendmmsg net/socket.c:2561 [inline]
 __se_sys_sendmmsg net/socket.c:2558 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2558
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000000000006229 -> 0x000000000000622a

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16508 Comm: syz-executor.5 Tainted: G        W         5.14.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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