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BUG: KCSAN: data-race in fill_mg_cmtime / shmem_mknod

write to 0xffff88810109f82c of 4 bytes by task 3739 on cpu 1:
 inode_set_mtime_to_ts include/linux/fs.h:1706 [inline]
 shmem_mknod+0x137/0x180 mm/shmem.c:3858
 shmem_create+0x34/0x50 mm/shmem.c:3917
 lookup_open fs/namei.c:3701 [inline]
 open_last_lookups fs/namei.c:3800 [inline]
 path_openat+0x1102/0x2170 fs/namei.c:4036
 do_filp_open+0x109/0x230 fs/namei.c:4066
 do_sys_openat2+0xa6/0x110 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+0xf2/0x120 fs/open.c:1455
 x64_sys_call+0x1af/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:258
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810109f82c of 4 bytes by task 3728 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+0x5b/0x260 fs/stat.c:55
 generic_fillattr+0x24a/0x340 fs/stat.c:99
 shmem_getattr+0x181/0x200 mm/shmem.c:1262
 vfs_getattr_nosec+0x143/0x1e0 fs/stat.c:210
 vfs_getattr fs/stat.c:259 [inline]
 vfs_statx_path fs/stat.c:296 [inline]
 vfs_statx+0x11a/0x380 fs/stat.c:353
 vfs_fstatat+0xe1/0x160 fs/stat.c:372
 __do_sys_newfstatat fs/stat.c:536 [inline]
 __se_sys_newfstatat+0x55/0x260 fs/stat.c:530
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:530
 x64_sys_call+0x2c22/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x009eca61 -> 0x013a8b5e

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 3728 Comm: udevd Not tainted 6.15.0-rc4-syzkaller-00051-g7a13c14ee59d #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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