[moderation] [fs?] KCSAN: data-race in fasync_remove_entry / kill_fasync (13)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c45323b7560e Merge tag 'mm-hotfixes-stable-2025-01-13-00-0..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13b45bc4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=1d9abea8414eb570
dashboard link: https://syzkaller.appspot.com/bug?extid=efbd8ba031ba43118d95
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/0d01636c1228/disk-c45323b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/bd568f5245f3/vmlinux-c45323b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b0ea6c9f50fc/bzImage-c45323b7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+efbd8b...@syzkaller.appspotmail.com

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

write to 0xffff888100627458 of 8 bytes by task 5742 on cpu 1:
fasync_remove_entry+0xd2/0x130 fs/fcntl.c:1005
fasync_helper+0x96/0xc0 fs/fcntl.c:1104
sock_fasync+0x5a/0xc0 net/socket.c:1433
__fput+0x662/0x6d0 fs/file_table.c:447
____fput+0x1c/0x30 fs/file_table.c:478
task_work_run+0x13a/0x1a0 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xa8/0x120 kernel/entry/common.c:218
do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100627458 of 8 bytes by task 5736 on cpu 0:
kill_fasync+0x24/0x170 fs/fcntl.c:1146
sock_wake_async+0xf5/0x120
sk_wake_async include/net/sock.h:2463 [inline]
unix_release_sock+0x45c/0x750 net/unix/af_unix.c:710
unix_release+0x57/0x80 net/unix/af_unix.c:1109
__sock_release net/socket.c:640 [inline]
sock_close+0x68/0x150 net/socket.c:1408
__fput+0x17a/0x6d0 fs/file_table.c:450
____fput+0x1c/0x30 fs/file_table.c:478
task_work_run+0x13a/0x1a0 kernel/task_work.c:239
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
exit_to_user_mode_loop kernel/entry/common.c:114 [inline]
exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
syscall_exit_to_user_mode+0xa8/0x120 kernel/entry/common.c:218
do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8881318fa390 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 5736 Comm: syz.0.747 Not tainted 6.13.0-rc7-syzkaller-00019-gc45323b7560e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
==================================================================


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[syzbot]

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