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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff8881053dfcc0 of 4 bytes by task 17550 on cpu 1:
 d_set_d_op+0xfb/0x1f0 fs/dcache.c:1792
 proc_ns_instantiate fs/proc/namespaces.c:114 [inline]
 proc_ns_dir_lookup+0x180/0x220 fs/proc/namespaces.c:172
 lookup_open fs/namei.c:3478 [inline]
 open_last_lookups fs/namei.c:3569 [inline]
 path_openat+0xc6f/0x1d40 fs/namei.c:3799
 do_filp_open+0xf6/0x200 fs/namei.c:3829
 do_sys_openat2+0xab/0x110 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1430
 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 0xffff8881053dfcc0 of 4 bytes by task 17551 on cpu 0:
 d_in_lookup include/linux/dcache.h:366 [inline]
 d_wait_lookup fs/dcache.c:2443 [inline]
 d_alloc_parallel+0x5f9/0xc60 fs/dcache.c:2531
 lookup_open fs/namei.c:3425 [inline]
 open_last_lookups fs/namei.c:3569 [inline]
 path_openat+0x658/0x1d40 fs/namei.c:3799
 do_filp_open+0xf6/0x200 fs/namei.c:3829
 do_sys_openat2+0xab/0x110 fs/open.c:1404
 do_sys_open fs/open.c:1419 [inline]
 __do_sys_openat fs/open.c:1435 [inline]
 __se_sys_openat fs/open.c:1430 [inline]
 __x64_sys_openat+0xf3/0x120 fs/open.c:1430
 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: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 17551 Comm: syz-executor.1 Not tainted 6.8.0-rc6-syzkaller-00238-g5ad3cb0ed525 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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