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BUG: KCSAN: data-race in skb_queue_tail / unix_dgram_peer_wake_me

write to 0xffff88812bf914e0 of 4 bytes by task 19246 on cpu 1:
 __skb_insert include/linux/skbuff.h:1933 [inline]
 __skb_queue_before include/linux/skbuff.h:2038 [inline]
 __skb_queue_tail include/linux/skbuff.h:2071 [inline]
 skb_queue_tail+0x80/0xa0 net/core/skbuff.c:3242
 unix_dgram_sendmsg+0xff2/0x1610 net/unix/af_unix.c:1798
 sock_sendmsg_nosec net/socket.c:654 [inline]
 sock_sendmsg net/socket.c:674 [inline]
 ____sys_sendmsg+0x360/0x4d0 net/socket.c:2350
 ___sys_sendmsg net/socket.c:2404 [inline]
 __sys_sendmmsg+0x315/0x4b0 net/socket.c:2490
 __do_sys_sendmmsg net/socket.c:2519 [inline]
 __se_sys_sendmmsg net/socket.c:2516 [inline]
 __x64_sys_sendmmsg+0x53/0x60 net/socket.c:2516
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812bf914e0 of 4 bytes by task 19264 on cpu 0:
 skb_queue_len include/linux/skbuff.h:1864 [inline]
 unix_recvq_full net/unix/af_unix.c:194 [inline]
 unix_dgram_peer_wake_me+0x19c/0x310 net/unix/af_unix.c:441
 unix_dgram_poll+0x2f3/0x3e0 net/unix/af_unix.c:2726
 sock_poll+0x23e/0x260 net/socket.c:1246
 vfs_poll include/linux/poll.h:90 [inline]
 ep_item_poll fs/eventpoll.c:846 [inline]
 ep_send_events fs/eventpoll.c:1683 [inline]
 ep_poll fs/eventpoll.c:1798 [inline]
 do_epoll_wait+0x6ad/0xf00 fs/eventpoll.c:2226
 __do_sys_epoll_wait fs/eventpoll.c:2238 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2233 [inline]
 __x64_sys_epoll_wait+0xf6/0x120 fs/eventpoll.c:2233
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x0000001e -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 19264 Comm: syz-executor.4 Not tainted 5.13.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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