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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff88813d3f7000 of 4 bytes by task 7224 on cpu 1:
 __d_instantiate+0x2cd/0x3c0 fs/dcache.c:1855
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:1899
 ext4_mkdir+0x5e5/0x740 fs/ext4/namei.c:3048
 vfs_mkdir+0x1ef/0x2f0 fs/namei.c:4126
 do_mkdirat+0x12f/0x2a0 fs/namei.c:4149
 __do_sys_mkdir fs/namei.c:4169 [inline]
 __se_sys_mkdir fs/namei.c:4167 [inline]
 __x64_sys_mkdir+0x44/0x50 fs/namei.c:4167
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813d3f7000 of 4 bytes by task 7226 on cpu 0:
 d_revalidate fs/namei.c:861 [inline]
 lookup_fast+0xd9/0x290 fs/namei.c:1642
 walk_component+0x3f/0x230 fs/namei.c:2001
 lookup_last fs/namei.c:2462 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2486
 filename_lookup+0x126/0x300 fs/namei.c:2515
 user_path_at_empty+0x42/0x120 fs/namei.c:2924
 user_path_at include/linux/namei.h:57 [inline]
 do_mount fs/namespace.c:3689 [inline]
 __do_sys_mount fs/namespace.c:3898 [inline]
 __se_sys_mount+0x24b/0x2d0 fs/namespace.c:3875
 __x64_sys_mount+0x67/0x80 fs/namespace.c:3875
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000 -> 0x00280040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7226 Comm: syz-executor.3 Not tainted 6.8.0-rc6-syzkaller-00250-g04b8076df253 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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