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BUG: KCSAN: data-race in fill_mg_cmtime / shmem_mknod

write to 0xffff88810449954c of 4 bytes by task 3296 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1706 [inline]
 shmem_mknod+0x136/0x180 mm/shmem.c:3858
 shmem_create+0x34/0x40 mm/shmem.c:3917
 lookup_open fs/namei.c:3701 [inline]
 open_last_lookups fs/namei.c:3800 [inline]
 path_openat+0xec8/0x2000 fs/namei.c:4036
 do_filp_open+0x115/0x240 fs/namei.c:4066
 do_sys_openat2+0xaa/0x110 fs/open.c:1429
 do_sys_open fs/open.c:1444 [inline]
 __do_sys_openat fs/open.c:1460 [inline]
 __se_sys_openat fs/open.c:1455 [inline]
 __x64_sys_openat+0xf8/0x120 fs/open.c:1455
 x64_sys_call+0x1ac/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810449954c of 4 bytes by task 3295 on cpu 0:
 inode_get_mtime_nsec include/linux/fs.h:1692 [inline]
 inode_get_mtime include/linux/fs.h:1698 [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:1262
 vfs_getattr_nosec+0x141/0x1d0 fs/stat.c:210
 vfs_getattr fs/stat.c:259 [inline]
 vfs_statx_path fs/stat.c:296 [inline]
 vfs_statx+0x145/0x2f0 fs/stat.c:353
 vfs_fstatat+0xd9/0x150 fs/stat.c:372
 __do_sys_newfstatat fs/stat.c:536 [inline]
 __se_sys_newfstatat+0x58/0x260 fs/stat.c:530
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:530
 x64_sys_call+0x2d6f/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc9/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0ac57e67 -> 0x0b6988d5

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3295 Comm: udevd Not tainted 6.15.0-rc3-syzkaller-00008-ga33b5a08cbbd #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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