[moderation] [fs?] KCSAN: data-race in setattr_copy / touch_atime

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c8ed9b5c02a5 Merge tag 'drm-fixes-2025-09-05' of https://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10055312580000
kernel config: https://syzkaller.appspot.com/x/.config?x=52ae2e92d7a28724
dashboard link: https://syzkaller.appspot.com/bug?extid=478376fef106d0c8d7f8
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/a74226e04a1d/disk-c8ed9b5c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/972f201c4d2f/vmlinux-c8ed9b5c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/f09bd3d00bee/bzImage-c8ed9b5c.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+478376...@syzkaller.appspotmail.com

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

write to 0xffff88811a66a3d0 of 4 bytes by task 3296 on cpu 0:
inode_set_atime_to_ts include/linux/fs.h:1687 [inline]
setattr_copy+0x253/0x4b0 fs/attr.c:359
shmem_setattr+0x566/0x840 mm/shmem.c:1375
notify_change+0x806/0x890 fs/attr.c:552
vfs_utimes+0x2fc/0x410 fs/utimes.c:66
do_utimes_path fs/utimes.c:99 [inline]
do_utimes+0x154/0x210 fs/utimes.c:140
__do_sys_utimensat fs/utimes.c:159 [inline]
__se_sys_utimensat fs/utimes.c:143 [inline]
__x64_sys_utimensat+0xc4/0x170 fs/utimes.c:143
x64_sys_call+0x2fba/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:281
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 0xffff88811a66a3d0 of 4 bytes by task 3293 on cpu 1:
inode_get_atime_nsec include/linux/fs.h:1672 [inline]
inode_get_atime include/linux/fs.h:1678 [inline]
inode_update_timestamps fs/inode.c:2031 [inline]
generic_update_time fs/inode.c:2056 [inline]
inode_update_time fs/inode.c:2076 [inline]
touch_atime+0x194/0x340 fs/inode.c:2148
do_readlinkat+0x134/0x320 fs/stat.c:589
__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: 0x103d880a -> 0x104a9a68

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3293 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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