[moderation] [fs?] KCSAN: data-race in d_lru_add / step_into (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5bbd9b249880 Merge tag 'v6.10-p4' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16366912980000
kernel config: https://syzkaller.appspot.com/x/.config?x=7e87b541dc1fc960
dashboard link: https://syzkaller.appspot.com/bug?extid=593f82c706a019d08270
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
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/ff5f8f9b9600/disk-5bbd9b24.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/9d83e00a503c/vmlinux-5bbd9b24.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1bf6e142ccb0/bzImage-5bbd9b24.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+593f82...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_lru_add / step_into

write to 0xffff88810781f0c0 of 4 bytes by task 12658 on cpu 1:
d_lru_add+0x45/0xe0 fs/dcache.c:426
retain_dentry fs/dcache.c:712 [inline]
fast_dput+0x26b/0x2b0 fs/dcache.c:799
dput+0x24/0xd0 fs/dcache.c:839
done_path_create fs/namei.c:3950 [inline]
do_mkdirat+0x139/0x2a0 fs/namei.c:4157
__do_sys_mkdirat fs/namei.c:4169 [inline]
__se_sys_mkdirat fs/namei.c:4167 [inline]
__x64_sys_mkdirat+0x50/0x60 fs/namei.c:4167
x64_sys_call+0x2ce5/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:259
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810781f0c0 of 4 bytes by task 12662 on cpu 0:
__d_entry_type include/linux/dcache.h:397 [inline]
d_is_symlink include/linux/dcache.h:427 [inline]
step_into+0x12f/0x810 fs/namei.c:1847
walk_component+0x169/0x230 fs/namei.c:2010
lookup_last fs/namei.c:2469 [inline]
path_lookupat+0x10a/0x2b0 fs/namei.c:2493
filename_lookup+0x127/0x300 fs/namei.c:2522
user_path_at_empty+0x42/0x120 fs/namei.c:2929
user_path_at include/linux/namei.h:58 [inline]
__do_sys_chdir fs/open.c:558 [inline]
__se_sys_chdir+0x4f/0x150 fs/open.c:552
__x64_sys_chdir+0x1f/0x30 fs/open.c:552
x64_sys_call+0x2b05/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:81
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00200000 -> 0x00280040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12662 Comm: syz.2.2860 Not tainted 6.10.0-rc5-syzkaller-00200-g5bbd9b249880 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================


---
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