syzbot

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BUG: KCSAN: data-race in d_alloc_parallel / d_set_d_op

read-write to 0xffff88811f314240 of 4 bytes by task 20684 on cpu 0:
 d_set_d_op+0xf0/0x1e0 fs/dcache.c:1932
 proc_pident_instantiate+0x164/0x180 fs/proc/base.c:2625
 proc_pident_lookup fs/proc/base.c:2648 [inline]
 proc_tgid_base_lookup+0x10c/0x180 fs/proc/base.c:3331
 __lookup_slow+0x182/0x250 fs/namei.c:1701
 lookup_slow+0x3c/0x60 fs/namei.c:1718
 walk_component+0x23d/0x280 fs/namei.c:2014
 link_path_walk+0x459/0x7a0
 path_openat+0x199/0x1b30 fs/namei.c:3649
 do_filp_open+0x105/0x220 fs/namei.c:3680
 do_sys_openat2+0xb5/0x2a0 fs/open.c:1278
 do_sys_open fs/open.c:1294 [inline]
 __do_sys_openat fs/open.c:1310 [inline]
 __se_sys_openat fs/open.c:1305 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1305
 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+0x46/0xb0

read to 0xffff88811f314240 of 4 bytes by task 20683 on cpu 1:
 d_in_lookup include/linux/dcache.h:356 [inline]
 d_wait_lookup fs/dcache.c:2582 [inline]
 d_alloc_parallel+0x655/0xcc0 fs/dcache.c:2670
 __lookup_slow+0x80/0x250 fs/namei.c:1686
 lookup_slow+0x3c/0x60 fs/namei.c:1718
 walk_component+0x23d/0x280 fs/namei.c:2014
 link_path_walk+0x459/0x7a0
 path_openat+0x199/0x1b30 fs/namei.c:3649
 do_filp_open+0x105/0x220 fs/namei.c:3680
 do_sys_openat2+0xb5/0x2a0 fs/open.c:1278
 do_sys_open fs/open.c:1294 [inline]
 __do_sys_openat fs/open.c:1310 [inline]
 __se_sys_openat fs/open.c:1305 [inline]
 __x64_sys_openat+0xef/0x110 fs/open.c:1305
 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+0x46/0xb0

value changed: 0x10000000 -> 0x1000000c

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 20683 Comm: syz-executor.4 Not tainted 5.19.0-rc3-syzkaller-00043-g3abc3ae553c7-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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