KCSAN: data-race in do_epoll_wait / do_epoll_wait

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: d25f27432f80 Merge tag 'arm-soc-fixes-5.15-3' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17059804b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=8a9d31400f5eedd8
dashboard link: https://syzkaller.appspot.com/bug?extid=bdd6e38a1ed5ee58d8bd
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.2
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+bdd6e3...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_epoll_wait / do_epoll_wait

write to 0xffff888102aa0358 of 8 bytes by task 484 on cpu 1:
INIT_LIST_HEAD include/linux/list.h:36 [inline]
list_splice_init include/linux/list.h:483 [inline]
ep_start_scan fs/eventpoll.c:615 [inline]
ep_send_events fs/eventpoll.c:1649 [inline]
ep_poll fs/eventpoll.c:1799 [inline]
do_epoll_wait+0x4f1/0xf10 fs/eventpoll.c:2227
do_epoll_pwait fs/eventpoll.c:2261 [inline]
__do_sys_epoll_pwait fs/eventpoll.c:2274 [inline]
__se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2268
__x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2268
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888102aa0358 of 8 bytes by task 482 on cpu 0:
list_empty_careful include/linux/list.h:319 [inline]
ep_events_available fs/eventpoll.c:374 [inline]
ep_poll fs/eventpoll.c:1790 [inline]
do_epoll_wait+0x26e/0xf10 fs/eventpoll.c:2227
do_epoll_pwait fs/eventpoll.c:2261 [inline]
__do_sys_epoll_pwait fs/eventpoll.c:2274 [inline]
__se_sys_epoll_pwait+0x12b/0x240 fs/eventpoll.c:2268
__x64_sys_epoll_pwait+0x74/0x80 fs/eventpoll.c:2268
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff888102aa0350 -> 0xffff888101d2bb98

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 482 Comm: syz-fuzzer Not tainted 5.15.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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