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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff88812c2d8d80 of 4 bytes by task 10990 on cpu 1:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_add_nondir+0x16c/0x190 fs/ext4/namei.c:2798
 ext4_create+0x20e/0x2f0 fs/ext4/namei.c:2839
 vfs_create+0x194/0x280 fs/namei.c:3198
 do_mknodat+0x2a4/0x410 fs/namei.c:4050
 __do_sys_mknodat fs/namei.c:4078 [inline]
 __se_sys_mknodat fs/namei.c:4075 [inline]
 __x64_sys_mknodat+0x62/0x70 fs/namei.c:4075
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88812c2d8d80 of 4 bytes by task 10995 on cpu 0:
 __d_entry_type include/linux/dcache.h:391 [inline]
 d_is_symlink include/linux/dcache.h:421 [inline]
 step_into+0x12f/0x800 fs/namei.c:1844
 open_last_lookups fs/namei.c:3588 [inline]
 path_openat+0x10da/0x1d30 fs/namei.c:3795
 do_filp_open+0xf6/0x200 fs/namei.c:3825
 do_sys_openat2+0xab/0x110 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_open fs/open.c:1427 [inline]
 __se_sys_open fs/open.c:1423 [inline]
 __x64_sys_open+0xe6/0x110 fs/open.c:1423
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000 -> 0x00480000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10995 Comm: syz-executor.0 Not tainted 6.8.0-rc1-syzkaller-00385-g4854cf9c61d0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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