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BUG: KCSAN: data-race in ip_finish_output2 / ip_finish_output2

read to 0xffff888124955c18 of 8 bytes by task 7260 on cpu 0:
 sock_confirm_neigh include/net/sock.h:1949 [inline]
 ip_finish_output2+0x3ab/0xe40 net/ipv4/ip_output.c:226
 __ip_finish_output net/ipv4/ip_output.c:308 [inline]
 __ip_finish_output+0x23a/0x490 net/ipv4/ip_output.c:290
 ip_finish_output+0x41/0x160 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:294 [inline]
 ip_output+0xdf/0x210 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125
 __ip_queue_xmit+0x3a8/0xa40 net/ipv4/ip_output.c:532
 ip_queue_xmit+0x45/0x60 include/net/ip.h:237
 __tcp_transmit_skb+0xe81/0x1d60 net/ipv4/tcp_output.c:1169
 tcp_transmit_skb net/ipv4/tcp_output.c:1185 [inline]
 tcp_write_xmit+0x9f3/0x3080 net/ipv4/tcp_output.c:2440
 __tcp_push_pending_frames+0x7b/0x1d0 net/ipv4/tcp_output.c:2616
 tcp_push_pending_frames include/net/tcp.h:1809 [inline]
 tcp_data_snd_check net/ipv4/tcp_input.c:5215 [inline]
 tcp_rcv_established+0xda0/0xf50 net/ipv4/tcp_input.c:5624
 tcp_v4_do_rcv+0x381/0x4e0 net/ipv4/tcp_ipv4.c:1561
 sk_backlog_rcv include/net/sock.h:945 [inline]
 __release_sock+0x135/0x1e0 net/core/sock.c:2435
 release_sock+0x61/0x160 net/core/sock.c:2951

write to 0xffff888124955c18 of 8 bytes by task 7241 on cpu 1:
 sock_confirm_neigh include/net/sock.h:1950 [inline]
 ip_finish_output2+0x3d6/0xe40 net/ipv4/ip_output.c:226
 __ip_finish_output net/ipv4/ip_output.c:308 [inline]
 __ip_finish_output+0x23a/0x490 net/ipv4/ip_output.c:290
 ip_finish_output+0x41/0x160 net/ipv4/ip_output.c:318
 NF_HOOK_COND include/linux/netfilter.h:294 [inline]
 ip_output+0xdf/0x210 net/ipv4/ip_output.c:432
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125
 __ip_queue_xmit+0x3a8/0xa40 net/ipv4/ip_output.c:532
 ip_queue_xmit+0x45/0x60 include/net/ip.h:237
 __tcp_transmit_skb+0xe81/0x1d60 net/ipv4/tcp_output.c:1169
 tcp_transmit_skb net/ipv4/tcp_output.c:1185 [inline]
 tcp_write_xmit+0x9f3/0x3080 net/ipv4/tcp_output.c:2440
 __tcp_push_pending_frames+0x7b/0x1d0 net/ipv4/tcp_output.c:2616
 tcp_push+0x1e9/0x3d0 net/ipv4/tcp.c:724
 tcp_sendmsg_locked+0x1d1e/0x1f30 net/ipv4/tcp.c:1403
 tcp_sendmsg+0x39/0x60 net/ipv4/tcp.c:1434

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 7241 Comm: sshd Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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