[moderation] [fs?] KCSAN: data-race in __dentry_kill / lookup_fast (14)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cf6fc5eefc5b Merge tag 's390-6.17-3' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=168f3fa2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=86a2212b48ce4ce2
dashboard link: https://syzkaller.appspot.com/bug?extid=1a16103352d77f31da30
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/891d252b566e/disk-cf6fc5ee.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ac2e760a0a02/vmlinux-cf6fc5ee.xz
kernel image: https://storage.googleapis.com/syzbot-assets/d7989cee25d9/bzImage-cf6fc5ee.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1a1610...@syzkaller.appspotmail.com

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

read-write to 0xffff888107286c00 of 4 bytes by task 3242 on cpu 1:
dentry_unlist fs/dcache.c:614 [inline]
__dentry_kill+0x230/0x4b0 fs/dcache.c:683
dput+0x5e/0xd0 fs/dcache.c:911
do_unlinkat+0x259/0x480 fs/namei.c:4653
__do_sys_unlink fs/namei.c:4696 [inline]
__se_sys_unlink fs/namei.c:4694 [inline]
__x64_sys_unlink+0x2e/0x40 fs/namei.c:4694
x64_sys_call+0x2dc0/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:88
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 0xffff888107286c00 of 4 bytes by task 2994 on cpu 0:
d_revalidate fs/namei.c:928 [inline]
lookup_fast+0xf0/0x320 fs/namei.c:1756
walk_component+0x3f/0x220 fs/namei.c:2125
lookup_last fs/namei.c:2630 [inline]
path_lookupat+0xfe/0x2a0 fs/namei.c:2654
filename_lookup+0x147/0x340 fs/namei.c:2683
do_readlinkat+0x7d/0x320 fs/stat.c:576
__do_sys_readlink fs/stat.c:613 [inline]
__se_sys_readlink fs/stat.c:610 [inline]
__x64_sys_readlink+0x47/0x60 fs/stat.c:610
x64_sys_call+0x28da/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:90
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: 0x00300080 -> 0x00004080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2994 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(voluntary)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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[syzbot]

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