syzbot

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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff88811acfe000 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_symlink+0x3a4/0x3b0 mm/shmem.c:4156
 vfs_symlink+0x106/0x220 fs/namei.c:5615
 filename_symlinkat+0xe8/0x2b0 fs/namei.c:5640
 __do_sys_symlink fs/namei.c:5667 [inline]
 __se_sys_symlink+0x42/0x1b0 fs/namei.c:5663
 __x64_sys_symlink+0x31/0x40 fs/namei.c:5663
 x64_sys_call+0x2465/0x3020 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811acfe000 of 4 bytes by task 3000 on cpu 1:
 d_revalidate fs/namei.c:1029 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1864
 walk_component fs/namei.c:2275 [inline]
 lookup_last fs/namei.c:2780 [inline]
 path_lookupat+0x15c/0x500 fs/namei.c:2804
 filename_lookup+0x190/0x390 fs/namei.c:2833
 do_readlinkat+0x74/0x2f0 fs/stat.c:571
 __do_sys_readlink fs/stat.c:605 [inline]
 __se_sys_readlink fs/stat.c:602 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:602
 x64_sys_call+0x2b51/0x3020 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000080 -> 0x08300080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3000 Comm: udevd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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