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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888138635e40 of 4 bytes by task 4884 on cpu 0:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2011
 d_instantiate_new+0x58/0xe0 fs/dcache.c:2055
 ext4_mkdir+0x5ff/0x760 fs/ext4/namei.c:2990
 vfs_mkdir+0x216/0x320 fs/namei.c:3975
 do_mkdirat+0x105/0x280 fs/namei.c:4001
 __do_sys_mkdir fs/namei.c:4021 [inline]
 __se_sys_mkdir fs/namei.c:4019 [inline]
 __x64_sys_mkdir+0x40/0x50 fs/namei.c:4019
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888138635e40 of 4 bytes by task 4885 on cpu 1:
 d_revalidate fs/namei.c:847 [inline]
 lookup_fast+0x172/0x360 fs/namei.c:1650
 walk_component+0x6b/0x280 fs/namei.c:2010
 link_path_walk+0x459/0x7a0
 path_lookupat+0x7b/0x2b0 fs/namei.c:2492
 filename_lookup+0x130/0x310 fs/namei.c:2522
 user_path_at_empty+0x3e/0x110 fs/namei.c:2895
 user_path_at include/linux/namei.h:57 [inline]
 __do_sys_chroot fs/open.c:562 [inline]
 __se_sys_chroot+0x56/0x190 fs/open.c:556
 __x64_sys_chroot+0x1b/0x20 fs/open.c:556
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x2b/0x70 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000000 -> 0x00280000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4885 Comm: syz-executor.4 Not tainted 5.19.0-rc6-syzkaller-00115-g4a57a8400075-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/29/2022
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