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BUG: KCSAN: data-race in do_epoll_wait / ep_poll_callback

write to 0xffff88811a51d0e8 of 4 bytes by task 13977 on cpu 1:
 ep_send_events fs/eventpoll.c:1706 [inline]
 ep_poll fs/eventpoll.c:1806 [inline]
 do_epoll_wait+0x833/0xf40 fs/eventpoll.c:2234
 __do_sys_epoll_wait fs/eventpoll.c:2246 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2241 [inline]
 __x64_sys_epoll_wait+0x119/0x140 fs/eventpoll.c:2241
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88811a51d0e8 of 4 bytes by task 13987 on cpu 0:
 ep_poll_callback+0x145/0x4e0 fs/eventpoll.c:1153
 __wake_up_common+0xbc/0x130 kernel/sched/wait.c:108
 __wake_up_common_lock kernel/sched/wait.c:138 [inline]
 __wake_up_sync_key+0x93/0xd0 kernel/sched/wait.c:205
 unix_write_space+0xc9/0x140 net/unix/af_unix.c:516
 sock_wfree+0xaf/0x150 net/core/sock.c:2296
 unix_destruct_scm+0x164/0x190 net/unix/scm.c:152
 skb_release_head_state+0xb3/0x1a0 net/core/skbuff.c:729
 skb_release_all net/core/skbuff.c:740 [inline]
 __kfree_skb+0x14/0x150 net/core/skbuff.c:756
 kfree_skb_reason+0x52/0x170 net/core/skbuff.c:776
 kfree_skb include/linux/skbuff.h:1114 [inline]
 skb_queue_purge+0xcd/0x120 net/core/skbuff.c:3275
 unix_dgram_disconnected net/unix/af_unix.c:530 [inline]
 unix_dgram_connect+0x555/0x800 net/unix/af_unix.c:1365
 __sys_connect_file net/socket.c:1900 [inline]
 __sys_connect+0x197/0x1b0 net/socket.c:1917
 __do_sys_connect net/socket.c:1927 [inline]
 __se_sys_connect net/socket.c:1924 [inline]
 __x64_sys_connect+0x3d/0x50 net/socket.c:1924
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x6000003c -> 0x60000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 13987 Comm: syz-executor.5 Not tainted 5.17.0-rc2-syzkaller-00316-g0457e5153e0e-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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