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BUG: KCSAN: data-race in iptunnel_xmit / iptunnel_xmit

read-write to 0xffff8880238af140 of 8 bytes by task 18240 on cpu 0:
 iptunnel_xmit_stats include/net/ip_tunnels.h:461 [inline]
 iptunnel_xmit+0x3f7/0x460 net/ipv4/ip_tunnel_core.c:87
 ip_tunnel_xmit+0x1084/0x11b0 net/ipv4/ip_tunnel.c:810
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x4d9/0x530 net/ipv4/ip_gre.c:648
 __netdev_start_xmit include/linux/netdevice.h:4718 [inline]
 netdev_start_xmit include/linux/netdevice.h:4732 [inline]
 xmit_one+0xb4/0x2a0 net/core/dev.c:3562
 dev_hard_start_xmit net/core/dev.c:3578 [inline]
 __dev_queue_xmit+0xead/0x14d0 net/core/dev.c:4137
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4170
 __bpf_tx_skb net/core/filter.c:2116 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2141 [inline]
 __bpf_redirect+0x544/0x750 net/core/filter.c:2164
 ____bpf_clone_redirect net/core/filter.c:2416 [inline]
 bpf_clone_redirect+0x168/0x1c0 net/core/filter.c:2388
 bpf_prog_bebbfe2050753572+0x56/0x438
 bpf_dispatcher_nop_func include/linux/bpf.h:644 [inline]
 bpf_test_run+0x266/0x450 net/bpf/test_run.c:50
 bpf_prog_test_run_skb+0x6f0/0xe70 net/bpf/test_run.c:581
 bpf_prog_test_run kernel/bpf/syscall.c:3126 [inline]
 __do_sys_bpf+0x39c9/0x9a80 kernel/bpf/syscall.c:4418
 __se_sys_bpf kernel/bpf/syscall.c:4358 [inline]
 __x64_sys_bpf+0x3d/0x50 kernel/bpf/syscall.c:4358
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read-write to 0xffff8880238af140 of 8 bytes by task 18266 on cpu 1:
 iptunnel_xmit_stats include/net/ip_tunnels.h:461 [inline]
 iptunnel_xmit+0x3f7/0x460 net/ipv4/ip_tunnel_core.c:87
 ip_tunnel_xmit+0x1084/0x11b0 net/ipv4/ip_tunnel.c:810
 __gre_xmit net/ipv4/ip_gre.c:466 [inline]
 ipgre_xmit+0x4d9/0x530 net/ipv4/ip_gre.c:648
 __netdev_start_xmit include/linux/netdevice.h:4718 [inline]
 netdev_start_xmit include/linux/netdevice.h:4732 [inline]
 xmit_one+0xb4/0x2a0 net/core/dev.c:3562
 dev_hard_start_xmit net/core/dev.c:3578 [inline]
 __dev_queue_xmit+0xead/0x14d0 net/core/dev.c:4137
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4170
 __bpf_tx_skb net/core/filter.c:2116 [inline]
 __bpf_redirect_no_mac net/core/filter.c:2141 [inline]
 __bpf_redirect+0x544/0x750 net/core/filter.c:2164
 ____bpf_clone_redirect net/core/filter.c:2416 [inline]
 bpf_clone_redirect+0x168/0x1c0 net/core/filter.c:2388
 bpf_prog_bebbfe2050753572+0x56/0x3bc
 bpf_dispatcher_nop_func include/linux/bpf.h:644 [inline]
 bpf_test_run+0x266/0x450 net/bpf/test_run.c:50
 bpf_prog_test_run_skb+0x6f0/0xe70 net/bpf/test_run.c:581
 bpf_prog_test_run kernel/bpf/syscall.c:3126 [inline]
 __do_sys_bpf+0x39c9/0x9a80 kernel/bpf/syscall.c:4418
 __se_sys_bpf kernel/bpf/syscall.c:4358 [inline]
 __x64_sys_bpf+0x3d/0x50 kernel/bpf/syscall.c:4358
 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: 18266 Comm: syz-executor.1 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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