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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff8881054a83c0 of 4 bytes by task 22246 on cpu 0:
 __d_instantiate+0x2cd/0x3c0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_add_nondir+0x16c/0x1a0 fs/ext4/namei.c:2797
 ext4_mknod+0x210/0x2f0 fs/ext4/namei.c:2872
 vfs_mknod+0x2d4/0x310 fs/namei.c:4009
 do_mknodat+0x27b/0x420
 __do_sys_mknod fs/namei.c:4092 [inline]
 __se_sys_mknod fs/namei.c:4090 [inline]
 __x64_sys_mknod+0x53/0x60 fs/namei.c:4090
 x64_sys_call+0x9e9/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:134
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881054a83c0 of 4 bytes by task 22247 on cpu 1:
 __follow_mount_rcu fs/namei.c:1485 [inline]
 handle_mounts fs/namei.c:1536 [inline]
 step_into+0xe7/0x810 fs/namei.c:1842
 open_last_lookups fs/namei.c:3597 [inline]
 path_openat+0x1118/0x1da0 fs/namei.c:3804
 do_filp_open+0xf7/0x200 fs/namei.c:3834
 do_sys_openat2+0xab/0x120 fs/open.c:1405
 do_sys_open fs/open.c:1420 [inline]
 __do_sys_open fs/open.c:1428 [inline]
 __se_sys_open fs/open.c:1424 [inline]
 __x64_sys_open+0xe6/0x110 fs/open.c:1424
 x64_sys_call+0x12d6/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:3
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00500000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22247 Comm: syz-executor.4 Not tainted 6.10.0-rc4-syzkaller-00164-g66cc544fd75c #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
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