[moderation] [fs?] KCSAN: data-race in ep_poll_callback / ep_try_send_events (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 372800cb95a3 Merge tag 'for-6.19-rc4-tag' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=179ba19a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=adceca945989c5733b95
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [bra...@kernel.org ja...@suse.cz linux-...@vger.kernel.org linux-...@vger.kernel.org vi...@zeniv.linux.org.uk]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8543bb0498db/disk-372800cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/66027c524d0e/vmlinux-372800cb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/2f88be755a57/bzImage-372800cb.xz

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

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

write to 0xffff88811c1eb6e8 of 4 bytes by task 11257 on cpu 0:
ep_send_events fs/eventpoll.c:1832 [inline]
ep_try_send_events+0x4f2/0x710 fs/eventpoll.c:1905
ep_poll fs/eventpoll.c:1970 [inline]
do_epoll_wait+0x371/0x940 fs/eventpoll.c:2461
do_epoll_pwait+0x54/0x150 fs/eventpoll.c:2491
__do_sys_epoll_pwait fs/eventpoll.c:2504 [inline]
__se_sys_epoll_pwait fs/eventpoll.c:2498 [inline]
__x64_sys_epoll_pwait+0x17d/0x1b0 fs/eventpoll.c:2498
x64_sys_call+0x153d/0x3000 arch/x86/include/generated/asm/syscalls_64.h:282
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811c1eb6e8 of 4 bytes by task 11258 on cpu 1:
ep_poll_callback+0x4a7/0x580 fs/eventpoll.c:1332
__wake_up_common kernel/sched/wait.c:108 [inline]
__wake_up_common_lock kernel/sched/wait.c:125 [inline]
__wake_up+0x66/0xb0 kernel/sched/wait.c:146
do_notify_pidfd kernel/signal.c:2157 [inline]
do_notify_parent+0x18c/0x560 kernel/signal.c:2185
exit_notify kernel/exit.c:758 [inline]
do_exit+0xbbc/0x1590 kernel/exit.c:983
__do_sys_exit kernel/exit.c:1079 [inline]
__se_sys_exit kernel/exit.c:1077 [inline]
__x64_sys_exit+0x1f/0x20 kernel/exit.c:1077
x64_sys_call+0x2fe7/0x3000 arch/x86/include/generated/asm/syscalls_64.h:61
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xca/0x2b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xe000203b -> 0xe0000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 11258 Comm: syz.1.3379 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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