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BUG: KCSAN: data-race in __d_instantiate / lookup_fast

read-write to 0xffff888140187480 of 4 bytes by task 16052 on cpu 0:
 __d_instantiate+0x2cd/0x3b0 fs/dcache.c:2011
 d_instantiate_new+0x5c/0xf0 fs/dcache.c:2055
 ext4_add_nondir+0x161/0x190 fs/ext4/namei.c:2797
 ext4_symlink+0x4c5/0x580 fs/ext4/namei.c:3431
 vfs_symlink+0xc2/0x1a0 fs/namei.c:4475
 do_symlinkat+0xe3/0x320 fs/namei.c:4501
 __do_sys_symlinkat fs/namei.c:4517 [inline]
 __se_sys_symlinkat fs/namei.c:4514 [inline]
 __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4514
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

read to 0xffff888140187480 of 4 bytes by task 16053 on cpu 1:
 d_revalidate fs/namei.c:858 [inline]
 lookup_fast+0xd9/0x290 fs/namei.c:1639
 walk_component+0x3f/0x230 fs/namei.c:1994
 lookup_last fs/namei.c:2455 [inline]
 path_lookupat+0x10a/0x2a0 fs/namei.c:2479
 filename_lookup+0x126/0x300 fs/namei.c:2508
 user_path_at_empty+0x42/0x110 fs/namei.c:2907
 do_readlinkat+0x92/0x210 fs/stat.c:477
 __do_sys_readlinkat fs/stat.c:504 [inline]
 __se_sys_readlinkat fs/stat.c:501 [inline]
 __x64_sys_readlinkat+0x53/0x60 fs/stat.c:501
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00080000 -> 0x00680040

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16053 Comm: syz-executor.4 Not tainted 6.4.0-rc3-syzkaller-00004-g421ca22e3138 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/28/2023
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