[moderation] [fs?] KCSAN: data-race in d_lru_del / dentry_kill

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 1dc18801be29 Merge tag 'i2c-7.2-part2' of git://git.kernel..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15b08356580000
kernel config: https://syzkaller.appspot.com/x/.config?x=da1374883fd3c788
dashboard link: https://syzkaller.appspot.com/bug?extid=f7859f6296c8de068452
compiler: Debian clang version 22.1.6 (++20260514074242+fc4aad7b5db3-1~exp1~20260514074407.73), Debian LLD 22.1.6
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/00169c4b2637/disk-1dc18801.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/3766ac1af734/vmlinux-1dc18801.xz
kernel image: https://storage.googleapis.com/syzbot-assets/cde5327c3733/bzImage-1dc18801.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f7859f...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_lru_del / dentry_kill

write to 0xffff888105d1b540 of 4 bytes by task 2979 on cpu 0:
d_lru_del+0x4c/0x100 fs/dcache.c:515
dentry_kill+0x10a/0x500 fs/dcache.c:821
finish_dput+0x16/0x1d0 fs/dcache.c:1001
dput+0x48/0x50 fs/dcache.c:1042
lookup_fast+0x29f/0x320 fs/namei.c:1886
walk_component fs/namei.c:2278 [inline]
lookup_last fs/namei.c:2789 [inline]
path_lookupat+0x120/0x4c0 fs/namei.c:2813
filename_lookup+0x18f/0x390 fs/namei.c:2842
do_readlinkat+0x74/0x2f0 fs/stat.c:571
__do_sys_readlink fs/stat.c:605 [inline]
__se_sys_readlink fs/stat.c:602 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:602
x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888105d1b540 of 4 bytes by task 29085 on cpu 1:
dentry_unlist fs/dcache.c:694 [inline]
dentry_kill+0x2d3/0x500 fs/dcache.c:840
finish_dput+0x16/0x1d0 fs/dcache.c:1001
dput+0x48/0x50 fs/dcache.c:1042
lookup_fast+0x29f/0x320 fs/namei.c:1886
walk_component fs/namei.c:2278 [inline]
lookup_last fs/namei.c:2789 [inline]
path_lookupat+0x120/0x4c0 fs/namei.c:2813
filename_lookup+0x18f/0x390 fs/namei.c:2842
vfs_statx+0x96/0x170 fs/stat.c:353
vfs_fstatat+0x118/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00140004 -> 0x00000004

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 29085 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(lazy)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
==================================================================


---
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