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BUG: KCSAN: data-race in __d_instantiate / step_into

read-write to 0xffff88810780a480 of 4 bytes by task 809 on cpu 1:
 __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_symlink+0x4dd/0x5a0 fs/ext4/namei.c:3433
 vfs_symlink+0xca/0x1d0 fs/namei.c:4489
 do_symlinkat+0xe3/0x350 fs/namei.c:4515
 __do_sys_symlinkat fs/namei.c:4531 [inline]
 __se_sys_symlinkat fs/namei.c:4528 [inline]
 __x64_sys_symlinkat+0x62/0x70 fs/namei.c:4528
 x64_sys_call+0x1e00/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:267
 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 0xffff88810780a480 of 4 bytes by task 811 on cpu 0:
 __d_entry_type include/linux/dcache.h:397 [inline]
 d_is_symlink include/linux/dcache.h:427 [inline]
 step_into+0x12f/0x810 fs/namei.c:1847
 walk_component fs/namei.c:2010 [inline]
 link_path_walk+0x49d/0x810 fs/namei.c:2331
 path_parentat fs/namei.c:2540 [inline]
 __filename_parentat+0x13c/0x3c0 fs/namei.c:2564
 filename_parentat fs/namei.c:2582 [inline]
 filename_create+0x77/0x2b0 fs/namei.c:3881
 do_mkdirat+0x63/0x2a0 fs/namei.c:4146
 __do_sys_mkdirat fs/namei.c:4169 [inline]
 __se_sys_mkdirat fs/namei.c:4167 [inline]
 __x64_sys_mkdirat+0x50/0x60 fs/namei.c:4167
 x64_sys_call+0x2ce5/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:259
 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: 0x00080000 -> 0x00680040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 811 Comm: syz-executor.3 Tainted: G        W          6.10.0-rc4-syzkaller-00148-g50736169ecc8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
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