syzbot

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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff88810556b900 of 4 bytes by task 3294 on cpu 1:
 fsnotify_update_flags include/linux/fsnotify_backend.h:-1 [inline]
 __d_instantiate+0x2c2/0x3b0 fs/dcache.c:1938
 d_instantiate+0x59/0x80 fs/dcache.c:1963
 shmem_symlink+0x3a7/0x3d0 mm/shmem.c:4200
 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+0x23cc/0x2ff0 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 0xffff88810556b900 of 4 bytes by task 2992 on cpu 0:
 __follow_mount_rcu fs/namei.c:1572 [inline]
 handle_mounts fs/namei.c:1623 [inline]
 step_into+0xe3/0x820 fs/namei.c:1967
 walk_component+0x162/0x220 fs/namei.c:2135
 lookup_last fs/namei.c:2630 [inline]
 path_lookupat+0xfe/0x2a0 fs/namei.c:2654
 filename_lookup+0x147/0x340 fs/namei.c:2683
 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+0x28da/0x2ff0 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: 0x00000080 -> 0x00300080

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2992 Comm: udevd Not tainted 6.17.0-rc1-syzkaller-00016-g8742b2d8935f #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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