[moderation] [fs?] KCSAN: data-race in __fput / setattr_copy (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 63804fed149a Linux 6.19-rc7
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=138c0322580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e27f4588a0f2183
dashboard link: https://syzkaller.appspot.com/bug?extid=d52b2a00b5d370a9566e
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/a01803567280/disk-63804fed.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2e8f54c26352/vmlinux-63804fed.xz
kernel image: https://storage.googleapis.com/syzbot-assets/aedebc96acfe/bzImage-63804fed.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d52b2a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __fput / setattr_copy

write to 0xffff88811d4f14d8 of 2 bytes by task 13364 on cpu 0:
setattr_copy+0x199/0x4a0 fs/attr.c:344
shmem_setattr+0x5be/0x7c0 mm/shmem.c:1357
notify_change+0x872/0x8f0 fs/attr.c:546
chmod_common+0x141/0x270 fs/open.c:647
do_fchmodat+0xa4/0x150 fs/open.c:694
__do_sys_chmod fs/open.c:718 [inline]
__se_sys_chmod fs/open.c:716 [inline]
__x64_sys_chmod+0x38/0x50 fs/open.c:716
x64_sys_call+0x2aaf/0x3000 arch/x86/include/generated/asm/syscalls_64.h:91
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811d4f14d8 of 2 bytes by task 13396 on cpu 1:
__fput+0x2b9/0x650 fs/file_table.c:469
____fput+0x1c/0x30 fs/file_table.c:496
task_work_run+0x130/0x1a0 kernel/task_work.c:233
resume_user_mode_work include/linux/resume_user_mode.h:50 [inline]
__exit_to_user_mode_loop kernel/entry/common.c:44 [inline]
exit_to_user_mode_loop+0x1f7/0x6f0 kernel/entry/common.c:75
__exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
do_syscall_64+0x1d3/0x2a0 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x41c0 -> 0x435e

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13396 Comm: syz.4.2293 Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup