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BUG: KCSAN: data-race in ip6_tnl_start_xmit / ip6_tnl_start_xmit

write to 0xffff8880afd4e130 of 8 bytes by task 942 on cpu 1:
 ip6_tnl_start_xmit+0x808/0xa00 net/ipv6/ip6_tunnel.c:1458
 __netdev_start_xmit include/linux/netdevice.h:4611 [inline]
 netdev_start_xmit include/linux/netdevice.h:4625 [inline]
 xmit_one+0xc0/0x310 net/core/dev.c:3556
 dev_hard_start_xmit net/core/dev.c:3572 [inline]
 __dev_queue_xmit+0xf00/0x15a0 net/core/dev.c:4131
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4164
 neigh_connected_output+0x24f/0x280 net/core/neighbour.c:1518
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0x97f/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x302/0x330 net/ipv6/ip6_output.c:143
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:153
 NF_HOOK_COND include/linux/netfilter.h:296 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:176
 dst_output include/net/dst.h:443 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6_send_skb+0x43/0xf0 net/ipv6/ip6_output.c:1865
 udp_v6_send_skb+0x7a3/0xa00 net/ipv6/udp.c:1175
 udpv6_sendmsg+0x1529/0x1780 net/ipv6/udp.c:1473
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:638
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmmsg+0x322/0x4b0 net/socket.c:2496
 __do_sys_sendmmsg net/socket.c:2525 [inline]
 __se_sys_sendmmsg net/socket.c:2522 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2522
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880afd4e130 of 8 bytes by task 908 on cpu 0:
 ip6_tnl_start_xmit+0x7f6/0xa00 net/ipv6/ip6_tunnel.c:1458
 __netdev_start_xmit include/linux/netdevice.h:4611 [inline]
 netdev_start_xmit include/linux/netdevice.h:4625 [inline]
 xmit_one+0xc0/0x310 net/core/dev.c:3556
 dev_hard_start_xmit net/core/dev.c:3572 [inline]
 __dev_queue_xmit+0xf00/0x15a0 net/core/dev.c:4131
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4164
 neigh_connected_output+0x24f/0x280 net/core/neighbour.c:1518
 neigh_output include/net/neighbour.h:509 [inline]
 ip6_finish_output2+0x97f/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x302/0x330 net/ipv6/ip6_output.c:143
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:153
 NF_HOOK_COND include/linux/netfilter.h:296 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:176
 dst_output include/net/dst.h:443 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6_send_skb+0x43/0xf0 net/ipv6/ip6_output.c:1865
 udp_v6_send_skb+0x7a3/0xa00 net/ipv6/udp.c:1175
 udpv6_sendmsg+0x1529/0x1780 net/ipv6/udp.c:1473
 inet6_sendmsg+0x5f/0x80 net/ipv6/af_inet6.c:638
 sock_sendmsg_nosec net/socket.c:652 [inline]
 sock_sendmsg net/socket.c:672 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2352
 ___sys_sendmsg net/socket.c:2406 [inline]
 __sys_sendmmsg+0x322/0x4b0 net/socket.c:2496
 __do_sys_sendmmsg net/socket.c:2525 [inline]
 __se_sys_sendmmsg net/socket.c:2522 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2522
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 908 Comm: syz-executor.1 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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