syzbot

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BUG: KCSAN: data-race in hsr_forward_skb / hsr_forward_skb

write to 0xffff88808e60e110 of 8 bytes by task 31646 on cpu 1:
 hsr_forward_skb+0x999/0xaf0 net/hsr/hsr_forward.c:546
 hsr_dev_xmit+0x56/0x80 net/hsr/hsr_device.c:220
 __netdev_start_xmit include/linux/netdevice.h:4636 [inline]
 netdev_start_xmit include/linux/netdevice.h:4650 [inline]
 xmit_one+0xc0/0x310 net/core/dev.c:3561
 dev_hard_start_xmit net/core/dev.c:3577 [inline]
 __dev_queue_xmit+0xf00/0x15a0 net/core/dev.c:4136
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4169
 neigh_connected_output+0x24f/0x280 net/core/neighbour.c:1518
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0x4e2/0xb60 net/ipv4/ip_output.c:229
 __ip_finish_output+0x395/0x3e0 net/ipv4/ip_output.c:307
 ip_finish_output+0x39/0x160 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:431
 dst_output include/net/dst.h:443 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb+0x6e/0xe0 net/ipv4/ip_output.c:1567
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:948
 udp_sendmsg+0x12a3/0x1560 net/ipv4/udp.c:1235
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:817
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2353
 ___sys_sendmsg net/socket.c:2407 [inline]
 __sys_sendmmsg+0x322/0x4b0 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg net/socket.c:2523 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2523
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88808e60e110 of 8 bytes by task 31648 on cpu 0:
 hsr_forward_skb+0x987/0xaf0 net/hsr/hsr_forward.c:546
 hsr_dev_xmit+0x56/0x80 net/hsr/hsr_device.c:220
 __netdev_start_xmit include/linux/netdevice.h:4636 [inline]
 netdev_start_xmit include/linux/netdevice.h:4650 [inline]
 xmit_one+0xc0/0x310 net/core/dev.c:3561
 dev_hard_start_xmit net/core/dev.c:3577 [inline]
 __dev_queue_xmit+0xf00/0x15a0 net/core/dev.c:4136
 dev_queue_xmit+0x13/0x20 net/core/dev.c:4169
 neigh_connected_output+0x24f/0x280 net/core/neighbour.c:1518
 neigh_output include/net/neighbour.h:509 [inline]
 ip_finish_output2+0x4e2/0xb60 net/ipv4/ip_output.c:229
 __ip_finish_output+0x395/0x3e0 net/ipv4/ip_output.c:307
 ip_finish_output+0x39/0x160 net/ipv4/ip_output.c:317
 NF_HOOK_COND include/linux/netfilter.h:290 [inline]
 ip_output+0xf6/0x1a0 net/ipv4/ip_output.c:431
 dst_output include/net/dst.h:443 [inline]
 ip_local_out net/ipv4/ip_output.c:126 [inline]
 ip_send_skb+0x6e/0xe0 net/ipv4/ip_output.c:1567
 udp_send_skb+0x62d/0x860 net/ipv4/udp.c:948
 udp_sendmsg+0x12a3/0x1560 net/ipv4/udp.c:1235
 inet_sendmsg+0x5f/0x80 net/ipv4/af_inet.c:817
 sock_sendmsg_nosec net/socket.c:651 [inline]
 sock_sendmsg net/socket.c:671 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2353
 ___sys_sendmsg net/socket.c:2407 [inline]
 __sys_sendmmsg+0x322/0x4b0 net/socket.c:2497
 __do_sys_sendmmsg net/socket.c:2526 [inline]
 __se_sys_sendmmsg net/socket.c:2523 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2523
 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: 0 PID: 31648 Comm: syz-executor.3 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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