==================================================================
BUG: KCSAN: data-race in ip6_tnl_start_xmit / ip6_tnl_start_xmit

write to 0xffff888021308150 of 8 bytes by task 9921 on cpu 0:
 ip6_tnl_start_xmit+0x81e/0xa10 net/ipv6/ip6_tunnel.c:1437
 __netdev_start_xmit include/linux/netdevice.h:4825 [inline]
 netdev_start_xmit include/linux/netdevice.h:4839 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3605
 dev_hard_start_xmit net/core/dev.c:3621 [inline]
 __dev_queue_xmit+0xf22/0x1580 net/core/dev.c:4194
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4227
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1520
 neigh_output include/net/neighbour.h:510 [inline]
 ip6_finish_output2+0x985/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x428/0x480 net/ipv6/ip6_output.c:182
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:448 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6_send_skb net/ipv6/ip6_output.c:1904 [inline]
 ip6_push_pending_frames+0xb6/0x170 net/ipv6/ip6_output.c:1924
 rawv6_push_pending_frames net/ipv6/raw.c:613 [inline]
 rawv6_sendmsg+0x128c/0x1330 net/ipv6/raw.c:956
 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+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888021308150 of 8 bytes by task 9930 on cpu 1:
 ip6_tnl_start_xmit+0x80c/0xa10 net/ipv6/ip6_tunnel.c:1437
 __netdev_start_xmit include/linux/netdevice.h:4825 [inline]
 netdev_start_xmit include/linux/netdevice.h:4839 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3605
 dev_hard_start_xmit net/core/dev.c:3621 [inline]
 __dev_queue_xmit+0xf22/0x1580 net/core/dev.c:4194
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4227
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1520
 neigh_output include/net/neighbour.h:510 [inline]
 ip6_finish_output2+0x985/0xb20 net/ipv6/ip6_output.c:117
 __ip6_finish_output+0x428/0x480 net/ipv6/ip6_output.c:182
 ip6_finish_output+0x39/0x160 net/ipv6/ip6_output.c:192
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip6_output+0x10e/0x210 net/ipv6/ip6_output.c:215
 dst_output include/net/dst.h:448 [inline]
 ip6_local_out+0x60/0x80 net/ipv6/output_core.c:179
 ip6_send_skb net/ipv6/ip6_output.c:1904 [inline]
 ip6_push_pending_frames+0xb6/0x170 net/ipv6/ip6_output.c:1924
 rawv6_push_pending_frames net/ipv6/raw.c:613 [inline]
 rawv6_sendmsg+0x128c/0x1330 net/ipv6/raw.c:956
 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+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9930 Comm: syz-executor.0 Not tainted 5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================