[moderation] [fs?] KCSAN: data-race in dentry_unlink_inode / path_openat (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 51512e22efe8 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1559bcea580000
kernel config: https://syzkaller.appspot.com/x/.config?x=84b3039e8461eef5
dashboard link: https://syzkaller.appspot.com/bug?extid=6475b58100630a5b37d9
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
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/412eaa5aa52e/disk-51512e22.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/36b6c4e7cef2/vmlinux-51512e22.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c026a5294394/bzImage-51512e22.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+6475b5...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in dentry_unlink_inode / path_openat

write to 0xffff88811ac419f0 of 8 bytes by task 5826 on cpu 0:
__d_clear_type_and_inode fs/dcache.c:420 [inline]
dentry_unlink_inode+0x65/0x260 fs/dcache.c:464
dentry_kill+0x184/0x500 fs/dcache.c:826
finish_dput+0x16/0x1d0 fs/dcache.c:1001
dput+0x48/0x50 fs/dcache.c:1042
end_renaming fs/namei.c:4122 [inline]
filename_renameat2+0x478/0x6a0 fs/namei.c:6190
__do_sys_rename fs/namei.c:6232 [inline]
__se_sys_rename+0x4a/0x1c0 fs/namei.c:6228
__x64_sys_rename+0x31/0x40 fs/namei.c:6228
x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
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 0xffff88811ac419f0 of 8 bytes by task 3287 on cpu 1:
step_into fs/namei.c:2141 [inline]
open_last_lookups fs/namei.c:4643 [inline]
path_openat+0x649/0x2000 fs/namei.c:4856
do_file_open+0x16c/0x290 fs/namei.c:4888
do_sys_openat2+0xa0/0x130 fs/open.c:1368
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1385
x64_sys_call+0x1e39/0x3020 arch/x86/include/generated/asm/syscalls_64.h:258
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: 0xffff88811f399bb0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3287 Comm: udevd Not tainted syzkaller #0 PREEMPT(lazy)
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