[moderation] [fs?] KCSAN: data-race in generic_fillattr / setattr_copy (6)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 7dff99b35460 Remove WARN_ALL_UNSEEDED_RANDOM kernel config..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11318202580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6b32b22d8934c136
dashboard link: https://syzkaller.appspot.com/bug?extid=eff3c7ecf7813729d2f6
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/30da51958513/disk-7dff99b3.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/8c35f9221ea0/vmlinux-7dff99b3.xz
kernel image: https://storage.googleapis.com/syzbot-assets/80305f3e627a/bzImage-7dff99b3.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+eff3c7...@syzkaller.appspotmail.com

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

write to 0xffff88811746154c of 4 bytes by task 3609 on cpu 1:
inode_set_mtime_to_ts include/linux/fs.h:1659 [inline]
setattr_copy+0x2de/0x4a0 fs/attr.c:363
shmem_setattr+0x5be/0x7c0 mm/shmem.c:1385
notify_change+0x872/0x8f0 fs/attr.c:556
vfs_utimes+0x2fc/0x440 fs/utimes.c:67
do_utimes_path fs/utimes.c:99 [inline]
do_utimes+0x14d/0x210 fs/utimes.c:139
__do_sys_utimensat fs/utimes.c:158 [inline]
__se_sys_utimensat fs/utimes.c:142 [inline]
__x64_sys_utimensat+0xc4/0x190 fs/utimes.c:142
x64_sys_call+0x2bca/0x3020 arch/x86/include/generated/asm/syscalls_64.h:281
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811746154c of 4 bytes by task 3306 on cpu 0:
inode_get_mtime_nsec include/linux/fs.h:1645 [inline]
inode_get_mtime include/linux/fs.h:1651 [inline]
generic_fillattr+0x20e/0x340 fs/stat.c:102
shmem_getattr+0x181/0x200 mm/shmem.c:1302
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr+0x48/0x60 fs/stat.c:262
vfs_statx_path+0x28/0x140 fs/stat.c:299
vfs_statx+0xc4/0x170 fs/stat.c:356
vfs_fstatat+0x118/0x170 fs/stat.c:373
__do_sys_newfstatat fs/stat.c:538 [inline]
__se_sys_newfstatat+0x55/0x3e0 fs/stat.c:532
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:532
x64_sys_call+0x2c64/0x3020 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x1e2411f4 -> 0x1fedd575

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3306 Comm: udevd Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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