KCSAN: data-race in ep_poll_callback / ep_send_events_proc (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: eccc8767 Merge branch 'fixes' of git://git.kernel.org/pub/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=154bac3a500000
kernel config: https://syzkaller.appspot.com/x/.config?x=671e27f23e60a67b
dashboard link: https://syzkaller.appspot.com/bug?extid=fd44a3737d292d288a68
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+fd44a3...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in ep_poll_callback / ep_send_events_proc

write to 0xffff888101535770 of 4 bytes by task 30160 on cpu 1:
ep_send_events_proc+0x433/0x5f0 fs/eventpoll.c:1757
ep_scan_ready_list+0x13e/0x330 fs/eventpoll.c:712
ep_send_events fs/eventpoll.c:1786 [inline]
ep_poll fs/eventpoll.c:1942 [inline]
do_epoll_wait+0x4b2/0x810 fs/eventpoll.c:2323
__do_sys_epoll_wait fs/eventpoll.c:2333 [inline]
__se_sys_epoll_wait fs/eventpoll.c:2330 [inline]
__x64_sys_epoll_wait+0x4d/0x60 fs/eventpoll.c:2330
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888101535770 of 4 bytes by task 30175 on cpu 0:
ep_poll_callback+0x417/0x510 fs/eventpoll.c:1283
__wake_up_common+0xbc/0x130 kernel/sched/wait.c:93
__wake_up_common_lock kernel/sched/wait.c:123 [inline]
__wake_up_sync_key+0x83/0xc0 kernel/sched/wait.c:190
unix_write_space+0xc9/0x140 net/unix/af_unix.c:464
sock_wfree+0xbf/0x150 net/core/sock.c:2033
unix_destruct_scm+0x164/0x190 net/unix/scm.c:150
skb_release_head_state+0xb3/0x170 net/core/skbuff.c:651
skb_release_all net/core/skbuff.c:662 [inline]
__kfree_skb+0x14/0x150 net/core/skbuff.c:678
kfree_skb+0x50/0x170 net/core/skbuff.c:696
unix_release_sock+0x505/0x650 net/unix/af_unix.c:568
unix_release+0x2f/0x50 net/unix/af_unix.c:859
__sock_release net/socket.c:596 [inline]
sock_close+0x6c/0x150 net/socket.c:1277
__fput+0x243/0x4d0 fs/file_table.c:281
____fput+0x11/0x20 fs/file_table.c:314
task_work_run+0x8e/0x110 kernel/task_work.c:151
tracehook_notify_resume include/linux/tracehook.h:188 [inline]
exit_to_user_mode_loop kernel/entry/common.c:164 [inline]
exit_to_user_mode_prepare+0x13c/0x170 kernel/entry/common.c:191
syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30175 Comm: syz-executor.5 Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.