syzbot

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BUG: KCSAN: data-race in __d_instantiate / path_lookupat

read-write to 0xffff888100414780 of 4 bytes by task 3289 on cpu 0:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2a8/0x390 fs/dcache.c:2149
 d_make_persistent+0x72/0x110 fs/dcache.c:2973
 shmem_symlink+0x386/0x3a0 mm/shmem.c:4068
 vfs_symlink+0xfd/0x220 fs/namei.c:5656
 filename_symlinkat+0xe8/0x2b0 fs/namei.c:5681
 __do_sys_symlink fs/namei.c:5708 [inline]
 __se_sys_symlink+0x42/0x1b0 fs/namei.c:5704
 __x64_sys_symlink+0x31/0x40 fs/namei.c:5704
 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+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888100414780 of 4 bytes by task 2979 on cpu 1:
 d_managed include/linux/dcache.h:433 [inline]
 step_into fs/namei.c:2140 [inline]
 walk_component fs/namei.c:2288 [inline]
 lookup_last fs/namei.c:2789 [inline]
 path_lookupat+0x19b/0x4c0 fs/namei.c:2813
 filename_lookup+0x18f/0x390 fs/namei.c:2842
 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+0x136/0x3c0 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: 2979 Comm: udevd Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
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