[moderation] [fs?] KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (2)

Hello,

syzbot found the following issue on:

HEAD commit: 38fec10eb60d Linux 6.14
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10a28de4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=32c6de65612481f2
dashboard link: https://syzkaller.appspot.com/bug?extid=3d0e00746449e812d008
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [[email protected] [email protected] [email protected] [email protected] [email protected]]

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/9b43355892f6/disk-38fec10e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/144dbf5ec8b7/vmlinux-38fec10e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/4e7f6f813346/bzImage-38fec10e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: [email protected]

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

write to 0xffff888104239834 of 4 bytes by task 8940 on cpu 0:
inode_set_mtime_to_ts include/linux/fs.h:1708 [inline]
simple_rename_timestamp+0x50/0xd0 fs/libfs.c:809
shmem_rename2+0x284/0x2c0 mm/shmem.c:4088
vfs_rename+0x875/0x9c0 fs/namei.c:5069
do_renameat2+0x6a3/0xa70 fs/namei.c:5226
__do_sys_rename fs/namei.c:5273 [inline]
__se_sys_rename fs/namei.c:5271 [inline]
__x64_sys_rename+0x58/0x70 fs/namei.c:5271
x64_sys_call+0x2b1c/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:83
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104239834 of 4 bytes by task 3486 on cpu 1:
inode_get_mtime_nsec include/linux/fs.h:1694 [inline]
inode_get_mtime include/linux/fs.h:1700 [inline]
fill_mg_cmtime+0x58/0x280 fs/stat.c:55
generic_fillattr+0x241/0x330 fs/stat.c:99
shmem_getattr+0x17b/0x200 mm/shmem.c:1249
vfs_getattr_nosec fs/stat.c:208 [inline]
vfs_getattr+0x172/0x1b0 fs/stat.c:246
vfs_statx_path fs/stat.c:283 [inline]
vfs_statx+0x12d/0x320 fs/stat.c:349
vfs_fstatat+0xe4/0x130 fs/stat.c:368
__do_sys_newfstatat fs/stat.c:532 [inline]
__se_sys_newfstatat+0x58/0x260 fs/stat.c:526
__x64_sys_newfstatat+0x55/0x70 fs/stat.c:526
x64_sys_call+0x236d/0x2dc0 arch/x86/include/generated/asm/syscalls_64.h:263
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x004e7d16 -> 0x0052745f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3486 Comm: udevd Not tainted 6.14.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
==================================================================
udevd[3486]: inotify_add_watch(7, /dev/loop1p7, 10) failed: No such file or directory


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