syzbot

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BUG: KCSAN: data-race in hsr_forward_skb / hsr_forward_skb

read to 0xffff888074641118 of 8 bytes by task 5838 on cpu 1:
 hsr_forward_skb+0x9a0/0x1160 net/hsr/hsr_forward.c:366
 hsr_dev_xmit+0x58/0x70 net/hsr/hsr_device.c:231
 __netdev_start_xmit include/linux/netdevice.h:4413 [inline]
 netdev_start_xmit include/linux/netdevice.h:4427 [inline]
 xmit_one net/core/dev.c:3199 [inline]
 dev_hard_start_xmit+0xef/0x430 net/core/dev.c:3215
 __dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792
 dev_queue_xmit+0x21/0x30 net/core/dev.c:3825
 neigh_connected_output+0x28a/0x2e0 net/core/neighbour.c:1519
 neigh_output include/net/neighbour.h:511 [inline]
 ip_finish_output2+0x4af/0xe40 net/ipv4/ip_output.c:228
 __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_mc_output+0x143/0x620 net/ipv4/ip_output.c:417
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125
 ip_send_skb+0x35/0xb0 net/ipv4/ip_output.c:1559
 udp_send_skb.isra.0+0x3ce/0x8c0 net/ipv4/udp.c:891
 udp_sendmsg+0x1568/0x1900 net/ipv4/udp.c:1178
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311
 __sys_sendmmsg+0x123/0x350 net/socket.c:2413
 __do_sys_sendmmsg net/socket.c:2442 [inline]
 __se_sys_sendmmsg net/socket.c:2439 [inline]
 __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff888074641118 of 8 bytes by task 5856 on cpu 0:
 hsr_forward_skb+0x9b4/0x1160 net/hsr/hsr_forward.c:366
 hsr_dev_xmit+0x58/0x70 net/hsr/hsr_device.c:231
 __netdev_start_xmit include/linux/netdevice.h:4413 [inline]
 netdev_start_xmit include/linux/netdevice.h:4427 [inline]
 xmit_one net/core/dev.c:3199 [inline]
 dev_hard_start_xmit+0xef/0x430 net/core/dev.c:3215
 __dev_queue_xmit+0x14ab/0x1b40 net/core/dev.c:3792
 dev_queue_xmit+0x21/0x30 net/core/dev.c:3825
 neigh_connected_output+0x28a/0x2e0 net/core/neighbour.c:1519
 neigh_output include/net/neighbour.h:511 [inline]
 ip_finish_output2+0x4af/0xe40 net/ipv4/ip_output.c:228
 __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_mc_output+0x143/0x620 net/ipv4/ip_output.c:417
 dst_output include/net/dst.h:436 [inline]
 ip_local_out+0x74/0x90 net/ipv4/ip_output.c:125
 ip_send_skb+0x35/0xb0 net/ipv4/ip_output.c:1559
 udp_send_skb.isra.0+0x3ce/0x8c0 net/ipv4/udp.c:891
 udp_sendmsg+0x1568/0x1900 net/ipv4/udp.c:1178
 inet_sendmsg+0x6d/0x90 net/ipv4/af_inet.c:807
 sock_sendmsg_nosec net/socket.c:637 [inline]
 sock_sendmsg+0x9f/0xc0 net/socket.c:657
 ___sys_sendmsg+0x2b7/0x5d0 net/socket.c:2311
 __sys_sendmmsg+0x123/0x350 net/socket.c:2413
 __do_sys_sendmmsg net/socket.c:2442 [inline]
 __se_sys_sendmmsg net/socket.c:2439 [inline]
 __x64_sys_sendmmsg+0x64/0x80 net/socket.c:2439
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5856 Comm: syz-executor.5 Not tainted 5.4.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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