[moderation] [fs?] KCSAN: data-race in d_invalidate / fast_dput (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: bc9ff192a6c9 Merge tag 'net-6.16-rc6' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1014ba8c580000
kernel config: https://syzkaller.appspot.com/x/.config?x=a2f5ccd29a82f8aa
dashboard link: https://syzkaller.appspot.com/bug?extid=963f8cfc89821433ef81
compiler: Debian clang version 20.1.7 (++20250616065708+6146a88f6049-1~exp1~20250616065826.132), Debian LLD 20.1.7
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/cd81278ad98c/disk-bc9ff192.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1fea20ae9800/vmlinux-bc9ff192.xz
kernel image: https://storage.googleapis.com/syzbot-assets/00054e9f79c3/bzImage-bc9ff192.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+963f8c...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in d_invalidate / fast_dput

write to 0xffff88811a980310 of 8 bytes by task 5415 on cpu 0:
__d_drop fs/dcache.c:575 [inline]
d_invalidate+0x5b/0x1c0 fs/dcache.c:1651
lookup_fast+0x296/0x320 fs/namei.c:1782
walk_component fs/namei.c:2134 [inline]
link_path_walk+0x4ba/0x900 fs/namei.c:2506
path_openat+0x1de/0x2170 fs/namei.c:4051
do_filp_open+0x109/0x230 fs/namei.c:4082
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1463
x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811a980310 of 8 bytes by task 4841 on cpu 1:
hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
d_unhashed include/linux/dcache.h:359 [inline]
retain_dentry fs/dcache.c:752 [inline]
fast_dput+0x5f/0x2c0 fs/dcache.c:848
dput+0x24/0xd0 fs/dcache.c:905
handle_mounts fs/namei.c:1640 [inline]
step_into+0x5b2/0x820 fs/namei.c:1976
walk_component fs/namei.c:2144 [inline]
link_path_walk+0x571/0x900 fs/namei.c:2506
path_openat+0x1de/0x2170 fs/namei.c:4051
do_filp_open+0x109/0x230 fs/namei.c:4082
do_sys_openat2+0xa6/0x110 fs/open.c:1437
do_sys_open fs/open.c:1452 [inline]
__do_sys_openat fs/open.c:1468 [inline]
__se_sys_openat fs/open.c:1463 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1463
x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0xffff8882375629f0 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4841 Comm: udevd Not tainted 6.16.0-rc5-syzkaller-00121-gbc9ff192a6c9 #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
==================================================================


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[syzbot]

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