[moderation] [fs?] KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 51a24b7deaae Merge tag 'trace-tools-v6.17-rc5' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15313f12580000
kernel config: https://syzkaller.appspot.com/x/.config?x=c7f65ba98bb01573
dashboard link: https://syzkaller.appspot.com/bug?extid=7e46087e8342e14910a8
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/d68c6049bbc0/disk-51a24b7d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ef1f5d9dfc12/vmlinux-51a24b7d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/7549561d646b/bzImage-51a24b7d.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7e4608...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp

write to 0xffff888103f7a6bc of 4 bytes by task 9083 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1722 [inline]
simple_rename_timestamp+0x53/0xd0 fs/libfs.c:821
shmem_rename2+0x251/0x290 mm/shmem.c:4139
vfs_rename+0x7f0/0xa40 fs/namei.c:5129
do_renameat2+0x557/0xa10 fs/namei.c:5278
__do_sys_rename fs/namei.c:5325 [inline]
__se_sys_rename fs/namei.c:5323 [inline]
__x64_sys_rename+0x58/0x70 fs/namei.c:5323
x64_sys_call+0x1f9/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:83
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 0xffff888103f7a6bc of 4 bytes by task 3604 on cpu 1:
inode_get_mtime_nsec include/linux/fs.h:1708 [inline]
inode_get_mtime include/linux/fs.h:1714 [inline]
fill_mg_cmtime+0x5b/0x260 fs/stat.c:55
generic_fillattr+0x24a/0x340 fs/stat.c:99
shmem_getattr+0x181/0x200 mm/shmem.c:1294
vfs_getattr_nosec+0x146/0x1e0 fs/stat.c:213
vfs_getattr fs/stat.c:262 [inline]
vfs_statx_path fs/stat.c:299 [inline]
vfs_statx+0x113/0x390 fs/stat.c:356
vfs_fstatat+0x115/0x170 fs/stat.c:375
__do_sys_newfstatat fs/stat.c:542 [inline]
__se_sys_newfstatat+0x55/0x260 fs/stat.c:536
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
x64_sys_call+0x135a/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:263
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: 0x04110bd8 -> 0x042b068d

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3604 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
==================================================================


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