[moderation] [fs?] KCSAN: data-race in fill_mg_cmtime / simple_rename_timestamp (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: dca922e019dd Merge tag 'xsa48x-7.1-tag' of git://git.kerne..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=171db896580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=7063dc5c0c5911eff5c6
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/ab9ecbab86ca/disk-dca922e0.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/184be882f3a7/vmlinux-dca922e0.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3237b546043a/bzImage-dca922e0.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7063dc...@syzkaller.appspotmail.com

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

write to 0xffff8881043f714c of 4 bytes by task 3285 on cpu 1:
inode_set_mtime_to_ts include/linux/fs.h:1660 [inline]
simple_rename_timestamp+0x53/0xd0 fs/libfs.c:840
shmem_rename2+0x2df/0x310 mm/shmem.c:4074
vfs_rename+0x97f/0xad0 fs/namei.c:6054
filename_renameat2+0x3b6/0x6e0 fs/namei.c:6172
__do_sys_rename fs/namei.c:6216 [inline]
__se_sys_rename+0x4a/0x1c0 fs/namei.c:6212
__x64_sys_rename+0x31/0x40 fs/namei.c:6212
x64_sys_call+0x2b3/0x3020 arch/x86/include/generated/asm/syscalls_64.h:83
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881043f714c of 4 bytes by task 3890 on cpu 0:
inode_get_mtime_nsec include/linux/fs.h:1646 [inline]
inode_get_mtime include/linux/fs.h:1652 [inline]
fill_mg_cmtime+0x5b/0x240 fs/stat.c:55
generic_fillattr+0x24a/0x340 fs/stat.c:99
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/0x3b0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x02fd159a -> 0x036ca54d

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3890 Comm: udevd Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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