[moderation] [fs?] KCSAN: data-race in drop_nlink / generic_fillattr (10)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 416f99c3b16f Merge tag 'driver-core-6.19-rc1' of git://git..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b026c2580000
kernel config: https://syzkaller.appspot.com/x/.config?x=68e2aa566f4b916e
dashboard link: https://syzkaller.appspot.com/bug?extid=d8fcddf719a374bbc9f2
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
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/b795aefada57/disk-416f99c3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/642270208071/vmlinux-416f99c3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b4c32cc091b5/bzImage-416f99c3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d8fcdd...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in drop_nlink / generic_fillattr

write to 0xffff88811f075af0 of 4 bytes by task 3311 on cpu 0:
drop_nlink+0x3d/0xa0 fs/inode.c:418
__simple_unlink fs/libfs.c:800 [inline]
simple_unlink+0x60/0x80 fs/libfs.c:814
shmem_unlink+0x12d/0x140 mm/shmem.c:3980
shmem_rename2+0x1a1/0x290 mm/shmem.c:4065
vfs_rename+0x97f/0xad0 fs/namei.c:5929
do_renameat2+0x383/0x810 fs/namei.c:6047
__do_sys_rename fs/namei.c:6090 [inline]
__se_sys_rename fs/namei.c:6088 [inline]
__x64_sys_rename+0x58/0x70 fs/namei.c:6088
x64_sys_call+0x24e/0x3000 arch/x86/include/generated/asm/syscalls_64.h:83
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811f075af0 of 4 bytes by task 3008 on cpu 1:
generic_fillattr+0xfb/0x340 fs/stat.c:91
shmem_getattr+0x181/0x200 mm/shmem.c:1274
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr fs/stat.c:262 [inline]
vfs_fstat fs/stat.c:281 [inline]
__do_sys_newfstat fs/stat.c:555 [inline]
__se_sys_newfstat+0x96/0x2e0 fs/stat.c:550
__x64_sys_newfstat+0x31/0x40 fs/stat.c:550
x64_sys_call+0x2c51/0x3000 arch/x86/include/generated/asm/syscalls_64.h:6
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3008 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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