[moderation] [fs?] KCSAN: data-race in __dentry_kill / lookup_fast (15)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 5dbeeb268b63 Merge tag 'driver-core-6.19-rc7' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17f3e05a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6c9e86480ac654d3
dashboard link: https://syzkaller.appspot.com/bug?extid=a173cff1ec72cee3d0a2
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/8a4a5a3502b5/disk-5dbeeb26.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/65e86e2ad6af/vmlinux-5dbeeb26.xz
kernel image: https://storage.googleapis.com/syzbot-assets/050ae083081a/bzImage-5dbeeb26.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+a173cf...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __dentry_kill / lookup_fast

read-write to 0xffff8881004980c0 of 4 bytes by task 3313 on cpu 0:
dentry_unlist fs/dcache.c:615 [inline]
__dentry_kill+0x230/0x4b0 fs/dcache.c:684
finish_dput+0x2b/0x200 fs/dcache.c:879
dput+0x52/0x60 fs/dcache.c:928
__fput+0x444/0x650 fs/file_table.c:476
fput_close_sync+0xad/0x190 fs/file_table.c:573
__do_sys_close fs/open.c:1573 [inline]
__se_sys_close fs/open.c:1558 [inline]
__x64_sys_close+0x55/0xf0 fs/open.c:1558
x64_sys_call+0x2c25/0x3000 arch/x86/include/generated/asm/syscalls_64.h:4
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 0xffff8881004980c0 of 4 bytes by task 4860 on cpu 1:
d_revalidate fs/namei.c:976 [inline]
lookup_fast+0xf0/0x320 fs/namei.c:1814
lookup_fast_for_open fs/namei.c:4486 [inline]
open_last_lookups fs/namei.c:4520 [inline]
path_openat+0x415/0x23c0 fs/namei.c:4793
do_filp_open+0x15d/0x280 fs/namei.c:4823
do_sys_openat2+0xa6/0x150 fs/open.c:1430
do_sys_open fs/open.c:1436 [inline]
__do_sys_openat fs/open.c:1452 [inline]
__se_sys_openat fs/open.c:1447 [inline]
__x64_sys_openat+0xf2/0x120 fs/open.c:1447
x64_sys_call+0x2b07/0x3000 arch/x86/include/generated/asm/syscalls_64.h:258
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

value changed: 0x00200080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4860 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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