syzbot

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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888107ba4780 of 4 bytes by task 3307 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2a8/0x390 fs/dcache.c:1987
 d_make_persistent+0x78/0x110 fs/dcache.c:2803
 shmem_mknod+0x15f/0x170 mm/shmem.c:3915
 shmem_mkdir+0x33/0x70 mm/shmem.c:3956
 vfs_mkdir+0x510/0x560 fs/namei.c:5139
 do_mkdirat+0x133/0x3b0 fs/namei.c:5173
 __do_sys_mkdir fs/namei.c:5200 [inline]
 __se_sys_mkdir fs/namei.c:5198 [inline]
 __x64_sys_mkdir+0x42/0x50 fs/namei.c:5198
 x64_sys_call+0x2f32/0x3000 arch/x86/include/generated/asm/syscalls_64.h:84
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888107ba4780 of 4 bytes by task 3306 on cpu 1:
 d_revalidate fs/namei.c:976 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1814
 walk_component fs/namei.c:2225 [inline]
 lookup_last fs/namei.c:2730 [inline]
 path_lookupat+0x15c/0x500 fs/namei.c:2754
 filename_lookup+0x190/0x390 fs/namei.c:2783
 vfs_statx+0x96/0x170 fs/stat.c:353
 vfs_fstatat+0x115/0x170 fs/stat.c:375
 __do_sys_newfstatat fs/stat.c:542 [inline]
 __se_sys_newfstatat+0x55/0x3e0 fs/stat.c:536
 __x64_sys_newfstatat+0x55/0x70 fs/stat.c:536
 x64_sys_call+0x111f/0x3000 arch/x86/include/generated/asm/syscalls_64.h:263
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000080 -> 0x08100080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3306 Comm: udevd Not tainted syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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udevd[3306]: inotify_add_watch(7, /dev/loop2p3, 10) failed: No such file or directory