syzbot

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BUG: KCSAN: data-race in ip_tunnel_xmit / ip_tunnel_xmit

write to 0xffff888026e34130 of 8 bytes by task 10267 on cpu 0:
 ip_tunnel_xmit+0xdd4/0x11c0 net/ipv4/ip_tunnel.c:814
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x4f5/0x550 net/ipv4/ip_gre.c:648
 __netdev_start_xmit include/linux/netdevice.h:4778 [inline]
 netdev_start_xmit include/linux/netdevice.h:4792 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3574
 dev_hard_start_xmit net/core/dev.c:3590 [inline]
 __dev_queue_xmit+0xf22/0x1570 net/core/dev.c:4151
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4184
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1521
 neigh_output include/net/neighbour.h:510 [inline]
 ip_finish_output2+0x8e6/0xba0 net/ipv4/ip_output.c:230
 __ip_finish_output+0x2f9/0x490 net/ipv4/ip_output.c:252
 ip_finish_output+0x39/0x160 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:441 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb+0x6e/0xe0 net/ipv4/ip_output.c:1568
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:947
 udp_sendmsg+0x12b0/0x1560 net/ipv4/udp.c:1234
 udpv6_sendmsg+0x94b/0x1790 net/ipv6/udp.c:1346
 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:2345
 ___sys_sendmsg net/socket.c:2399 [inline]
 __sys_sendmmsg+0x335/0x4b0 net/socket.c:2489
 __do_sys_sendmmsg net/socket.c:2518 [inline]
 __se_sys_sendmmsg net/socket.c:2515 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2515
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888026e34130 of 8 bytes by task 10298 on cpu 1:
 ip_tunnel_xmit+0xdc2/0x11c0 net/ipv4/ip_tunnel.c:814
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x4f5/0x550 net/ipv4/ip_gre.c:648
 __netdev_start_xmit include/linux/netdevice.h:4778 [inline]
 netdev_start_xmit include/linux/netdevice.h:4792 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3574
 dev_hard_start_xmit net/core/dev.c:3590 [inline]
 __dev_queue_xmit+0xf22/0x1570 net/core/dev.c:4151
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4184
 neigh_connected_output+0x264/0x290 net/core/neighbour.c:1521
 neigh_output include/net/neighbour.h:510 [inline]
 ip_finish_output2+0x8e6/0xba0 net/ipv4/ip_output.c:230
 __ip_finish_output+0x2f9/0x490 net/ipv4/ip_output.c:252
 ip_finish_output+0x39/0x160 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:441 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb+0x6e/0xe0 net/ipv4/ip_output.c:1568
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:947
 udp_sendmsg+0x12b0/0x1560 net/ipv4/udp.c:1234
 udpv6_sendmsg+0x94b/0x1790 net/ipv6/udp.c:1346
 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:2345
 ___sys_sendmsg net/socket.c:2399 [inline]
 __sys_sendmmsg+0x335/0x4b0 net/socket.c:2489
 __do_sys_sendmmsg net/socket.c:2518 [inline]
 __se_sys_sendmmsg net/socket.c:2515 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2515
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 10298 Comm: syz-executor.3 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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