[moderation] [fs?] KCSAN: data-race in fasync_remove_entry / kill_fasync (14)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cf6fc5eefc5b Merge tag 's390-6.17-3' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10063fa2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=86a2212b48ce4ce2
dashboard link: https://syzkaller.appspot.com/bug?extid=d79f3e4e547e351581df
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
CC: [alex....@gmail.com bra...@kernel.org chuck...@oracle.com ja...@suse.cz jla...@kernel.org 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/891d252b566e/disk-cf6fc5ee.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ac2e760a0a02/vmlinux-cf6fc5ee.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d7989cee25d9/bzImage-cf6fc5ee.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d79f3e...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fasync_remove_entry / kill_fasync

write to 0xffff888104a1fbd8 of 8 bytes by task 6197 on cpu 0:
fasync_remove_entry+0xcc/0x120 fs/fcntl.c:1005
fasync_helper+0x97/0xc0 fs/fcntl.c:1104
pipe_fasync+0xce/0x150 fs/pipe.c:756
__fput+0x5e3/0x650 fs/file_table.c:465
____fput+0x1c/0x30 fs/file_table.c:496
task_work_run+0x131/0x1a0 kernel/task_work.c:227
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop+0xe4/0x100 kernel/entry/common.c:43
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104a1fbd8 of 8 bytes by task 6192 on cpu 1:
kill_fasync+0x22/0x170 fs/fcntl.c:1146
anon_pipe_read+0x6a2/0x750 fs/pipe.c:402
do_iter_readv_writev+0x499/0x540 fs/read_write.c:-1
vfs_readv+0x1ea/0x690 fs/read_write.c:1018
do_readv+0xe7/0x210 fs/read_write.c:1080
__do_sys_readv fs/read_write.c:1165 [inline]
__se_sys_readv fs/read_write.c:1162 [inline]
__x64_sys_readv+0x45/0x50 fs/read_write.c:1162
x64_sys_call+0x29f8/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:20
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff88811a325270 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6192 Comm: syz.4.901 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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[syzbot]

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