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BUG: KCSAN: data-race in iptunnel_xmit / iptunnel_xmit

write to 0xffff88813b0b5160 of 8 bytes by task 10667 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:459 [inline]
 iptunnel_xmit+0x422/0x4a0 net/ipv4/ip_tunnel_core.c:87
 ip_tunnel_xmit+0xf2a/0x11c0 net/ipv4/ip_tunnel.c:804
 __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:4823 [inline]
 netdev_start_xmit include/linux/netdevice.h:4837 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3593
 dev_hard_start_xmit net/core/dev.c:3609 [inline]
 __dev_queue_xmit+0xf22/0x1580 net/core/dev.c:4182
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4215
 __bpf_tx_skb net/core/filter.c:2116 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2141 [inline]
 __bpf_redirect+0x49c/0x7a0 net/core/filter.c:2164
 ____bpf_clone_redirect net/core/filter.c:2448 [inline]
 bpf_clone_redirect+0x168/0x1c0 net/core/filter.c:2420
 bpf_prog_24310864cecaea99+0x56/0x2f8
 bpf_dispatcher_nop_func include/linux/bpf.h:644 [inline]
 bpf_test_run+0x27d/0x440 net/bpf/test_run.c:50
 bpf_prog_test_run_skb+0x714/0xe90 net/bpf/test_run.c:582
 bpf_prog_test_run kernel/bpf/syscall.c:3127 [inline]
 __do_sys_bpf+0x3971/0x9990 kernel/bpf/syscall.c:4406
 __se_sys_bpf kernel/bpf/syscall.c:4346 [inline]
 __x64_sys_bpf+0x3d/0x50 kernel/bpf/syscall.c:4346
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88813b0b5160 of 8 bytes by task 10662 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:459 [inline]
 iptunnel_xmit+0x410/0x4a0 net/ipv4/ip_tunnel_core.c:87
 ip_tunnel_xmit+0xf2a/0x11c0 net/ipv4/ip_tunnel.c:804
 __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:4823 [inline]
 netdev_start_xmit include/linux/netdevice.h:4837 [inline]
 xmit_one+0xf9/0x2e0 net/core/dev.c:3593
 dev_hard_start_xmit net/core/dev.c:3609 [inline]
 __dev_queue_xmit+0xf22/0x1580 net/core/dev.c:4182
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4215
 __bpf_tx_skb net/core/filter.c:2116 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2141 [inline]
 __bpf_redirect+0x49c/0x7a0 net/core/filter.c:2164
 ____bpf_clone_redirect net/core/filter.c:2448 [inline]
 bpf_clone_redirect+0x168/0x1c0 net/core/filter.c:2420
 bpf_prog_589f4463ab771ece+0x56/0x300
 bpf_dispatcher_nop_func include/linux/bpf.h:644 [inline]
 bpf_test_run+0x27d/0x440 net/bpf/test_run.c:50
 bpf_prog_test_run_skb+0x714/0xe90 net/bpf/test_run.c:582
 bpf_prog_test_run kernel/bpf/syscall.c:3127 [inline]
 __do_sys_bpf+0x3971/0x9990 kernel/bpf/syscall.c:4406
 __se_sys_bpf kernel/bpf/syscall.c:4346 [inline]
 __x64_sys_bpf+0x3d/0x50 kernel/bpf/syscall.c:4346
 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: 0 PID: 10662 Comm: syz-executor.0 Not tainted 5.12.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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