[syzbot] [fs?] KCSAN: data-race in fill_mg_cmtime / inode_set_ctime_to_ts

[syzbot <syzbot+8091e831a26b0f999002@syzkaller.appspotmail.com>]

Hello,

syzbot found the following issue on:

HEAD commit:    6916d5703ddf Merge tag 'drm-fixes-2026-05-16' of https://g..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=164de8a6580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=2e40c0f41e01837e
dashboard link: https://syzkaller.appspot.com/bug?extid=8091e831a26b0f999002
compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68f41c193b0d/disk-6916d570.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/b43a9332252c/vmlinux-6916d570.xz
kernel image: https://storage.googleapis.com/syzbot-assets/6d9ea22a0feb/bzImage-6916d570.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+8091e831a26b0f999002@syzkaller.appspotmail.com

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

write to 0xffff888103f6ee90 of 8 bytes by task 9889 on cpu 1:
 inode_set_ctime_to_ts+0x8f/0x170 fs/inode.c:2771
 __simple_unlink fs/libfs.c:792 [inline]
 simple_unlink+0x38/0x80 fs/libfs.c:807
 shmem_unlink+0x12d/0x140 mm/shmem.c:3981
 vfs_unlink+0x1c7/0x490 fs/namei.c:5498
 filename_unlinkat+0x1e2/0x410 fs/namei.c:5568
 __do_sys_unlink fs/namei.c:5603 [inline]
 __se_sys_unlink+0x2b/0xe0 fs/namei.c:5600
 __x64_sys_unlink+0x1f/0x30 fs/namei.c:5600
 x64_sys_call+0x2eb6/0x3020 arch/x86/include/generated/asm/syscalls_64.h:88
 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 0xffff888103f6ee90 of 8 bytes by task 3291 on cpu 0:
 fill_mg_cmtime+0x86/0x240 fs/stat.c:56
 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: 0x0000000077359407 -> 0x0000000077359408

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3291 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
==================================================================


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