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BUG: KCSAN: data-race in ip_finish_output2 / ip_finish_output2

read to 0xffff8880b1191c18 of 8 bytes by interrupt 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
 sctp_v4_xmit+0xf4/0x110 net/sctp/protocol.c:976
 sctp_packet_transmit+0x111b/0x1760 net/sctp/output.c:629
 sctp_outq_flush_transports net/sctp/outqueue.c:1146 [inline]
 sctp_outq_flush+0x1e9/0x14c0 net/sctp/outqueue.c:1194
 sctp_outq_uncork+0x64/0x80 net/sctp/outqueue.c:757
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1781 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1184 [inline]
 sctp_do_sm+0x36a/0x2ef0 net/sctp/sm_sideeffect.c:1155
 sctp_generate_heartbeat_event+0x137/0x200 net/sctp/sm_sideeffect.c:391
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404
 expire_timers kernel/time/timer.c:1449 [inline]
 __run_timers kernel/time/timer.c:1773 [inline]
 __run_timers kernel/time/timer.c:1740 [inline]
 run_timer_softirq+0xcb8/0xd20 kernel/time/timer.c:1786

write to 0xffff8880b1191c18 of 8 bytes by interrupt 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
 sctp_v4_xmit+0xf4/0x110 net/sctp/protocol.c:976
 sctp_packet_transmit+0x111b/0x1760 net/sctp/output.c:629
 sctp_outq_flush_transports net/sctp/outqueue.c:1146 [inline]
 sctp_outq_flush+0x1e9/0x14c0 net/sctp/outqueue.c:1194
 sctp_outq_uncork+0x64/0x80 net/sctp/outqueue.c:757
 sctp_cmd_interpreter net/sctp/sm_sideeffect.c:1781 [inline]
 sctp_side_effects net/sctp/sm_sideeffect.c:1184 [inline]
 sctp_do_sm+0x36a/0x2ef0 net/sctp/sm_sideeffect.c:1155
 sctp_generate_heartbeat_event+0x137/0x200 net/sctp/sm_sideeffect.c:391
 call_timer_fn+0x5f/0x2f0 kernel/time/timer.c:1404

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 0 Comm: swapper/1 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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