syzbot

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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888100718f00 of 4 bytes by task 3527 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2c2/0x3b0 fs/dcache.c:1922
 d_instantiate+0x59/0x80 fs/dcache.c:1947
 shmem_symlink+0x3a7/0x3d0 mm/shmem.c:4132
 vfs_symlink+0xd4/0x1e0 fs/namei.c:4730
 do_symlinkat+0xc7/0x3c0 fs/namei.c:4756
 __do_sys_symlink fs/namei.c:4777 [inline]
 __se_sys_symlink fs/namei.c:4775 [inline]
 __x64_sys_symlink+0x50/0x60 fs/namei.c:4775
 x64_sys_call+0x2d8d/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:89
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100718f00 of 4 bytes by task 3009 on cpu 1:
 d_revalidate fs/namei.c:928 [inline]
 lookup_fast+0xf0/0x320 fs/namei.c:1765
 walk_component+0x3f/0x220 fs/namei.c:2134
 lookup_last fs/namei.c:2639 [inline]
 path_lookupat+0xfe/0x2a0 fs/namei.c:2663
 filename_lookup+0x147/0x340 fs/namei.c:2692
 do_readlinkat+0x7d/0x320 fs/stat.c:576
 __do_sys_readlink fs/stat.c:613 [inline]
 __se_sys_readlink fs/stat.c:610 [inline]
 __x64_sys_readlink+0x47/0x60 fs/stat.c:610
 x64_sys_call+0x2cf3/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:90
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000008 -> 0x00300008

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3009 Comm: udevd Not tainted 6.15.0-syzkaller-03645-g3d413f0cfd7e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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