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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff888109911300 of 4 bytes by task 13435 on cpu 0:
 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_mknod+0x153/0x180 mm/shmem.c:3864
 vfs_mknod+0x2ce/0x310 fs/namei.c:4322
 do_mknodat+0x283/0x610 fs/namei.c:-1
 __do_sys_mknod fs/namei.c:4405 [inline]
 __se_sys_mknod fs/namei.c:4403 [inline]
 __x64_sys_mknod+0x51/0x60 fs/namei.c:4403
 x64_sys_call+0x2d56/0x3000 arch/x86/include/generated/asm/syscalls_64.h:134
 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 0xffff888109911300 of 4 bytes by task 13436 on cpu 1:
 __d_entry_type include/linux/dcache.h:414 [inline]
 d_is_symlink include/linux/dcache.h:444 [inline]
 step_into+0x12f/0x7f0 fs/namei.c:1994
 open_last_lookups fs/namei.c:3922 [inline]
 path_openat+0x13e8/0x2170 fs/namei.c:4131
 do_filp_open+0x109/0x230 fs/namei.c:4161
 do_sys_openat2+0xa6/0x110 fs/open.c:1437
 do_sys_open fs/open.c:1452 [inline]
 __do_sys_open fs/open.c:1460 [inline]
 __se_sys_open fs/open.c:1456 [inline]
 __x64_sys_open+0xe6/0x110 fs/open.c:1456
 x64_sys_call+0x1457/0x3000 arch/x86/include/generated/asm/syscalls_64.h:3
 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 -> 0x00280080

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13436 Comm: syz.0.3460 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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