KCSAN: data-race in ep_poll_callback / ep_send_events

Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in ep_poll_callback / ep_send_events_proc (2) fs				2	1262d	1234d	0/26	auto-closed as invalid on 2020/12/22 14:13

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BUG: KCSAN: data-race in ep_poll_callback / ep_send_events_proc

write to 0xffff88812b1840f0 of 4 bytes by task 26315 on cpu 1:
 ep_send_events_proc+0x1d9/0x5a0 fs/eventpoll.c:1759
 ep_scan_ready_list.constprop.0+0x190/0x430 fs/eventpoll.c:714
 ep_send_events fs/eventpoll.c:1788 [inline]
 ep_poll+0xe2/0x910 fs/eventpoll.c:1925
 do_epoll_wait+0x15a/0x180 fs/eventpoll.c:2320
 __do_sys_epoll_wait fs/eventpoll.c:2330 [inline]
 __se_sys_epoll_wait fs/eventpoll.c:2327 [inline]
 __x64_sys_epoll_wait+0x5a/0x70 fs/eventpoll.c:2327
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812b1840f0 of 4 bytes by task 26301 on cpu 0:
 ep_poll_callback+0x177/0x6c0 fs/eventpoll.c:1285
 __wake_up_common+0x76/0x180 kernel/sched/wait.c:93
 __wake_up_common_lock+0x77/0xb0 kernel/sched/wait.c:123
 unix_write_space+0x10b/0x180 net/unix/af_unix.c:464
 sock_wfree+0x13e/0x1b0 net/core/sock.c:1969
 unix_destruct_scm+0xd2/0x100 net/unix/scm.c:149
 skb_release_head_state+0xb0/0x180 net/core/skbuff.c:651
 skb_release_all+0x1b/0x50 net/core/skbuff.c:662
 __kfree_skb net/core/skbuff.c:678 [inline]
 kfree_skb net/core/skbuff.c:696 [inline]
 kfree_skb+0x93/0x200 net/core/skbuff.c:690
 unix_release_sock+0x304/0x670 net/unix/af_unix.c:568
 unix_release+0x3a/0x60 net/unix/af_unix.c:867
 __sock_release+0x85/0x160 net/socket.c:605
 sock_close+0x1f/0x30 net/socket.c:1283
 __fput+0x1e9/0x500 fs/file_table.c:280
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xba/0x120 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26301 Comm: syz-executor.0 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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