syzbot

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BUG: KCSAN: data-race in __d_drop / __d_lookup

write to 0xffff888101fb7790 of 8 bytes by task 8403 on cpu 0:
 __hlist_bl_del include/linux/list_bl.h:128 [inline]
 ___d_drop fs/dcache.c:490 [inline]
 __d_drop+0x114/0x240 fs/dcache.c:497
 d_invalidate+0x4a/0x1a0 fs/dcache.c:1677
 proc_invalidate_siblings_dcache+0x1e3/0x2d0 fs/proc/inode.c:150
 proc_flush_pid+0x16/0x20 fs/proc/base.c:3326
 release_task+0xa9f/0xb90 kernel/exit.c:222
 wait_task_zombie kernel/exit.c:1107 [inline]
 wait_consider_task+0x104f/0x18e0 kernel/exit.c:1334
 do_wait_thread kernel/exit.c:1397 [inline]
 do_wait+0x1b1/0x4e0 kernel/exit.c:1468
 kernel_wait4+0x13c/0x1a0 kernel/exit.c:1630
 __do_sys_wait4 kernel/exit.c:1658 [inline]
 __se_sys_wait4 kernel/exit.c:1654 [inline]
 __x64_sys_wait4+0x7a/0x100 kernel/exit.c:1654
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888101fb7790 of 8 bytes by task 22533 on cpu 1:
 hlist_bl_unhashed include/linux/list_bl.h:54 [inline]
 d_unhashed include/linux/dcache.h:339 [inline]
 __d_lookup+0x14d/0x3b0 fs/dcache.c:2403
 lookup_fast+0x67/0x370 fs/namei.c:1502
 walk_component+0x5c/0x350 fs/namei.c:1857
 link_path_walk+0x491/0x760 fs/namei.c:2182
 path_lookupat+0x7b/0x560 fs/namei.c:2335
 filename_lookup+0xf2/0x380 fs/namei.c:2369
 user_path_at_empty+0x3b/0x50 fs/namei.c:2649
 user_path_at include/linux/namei.h:59 [inline]
 do_faccessat+0x260/0x500 fs/open.c:423
 __do_sys_access fs/open.c:482 [inline]
 __se_sys_access fs/open.c:480 [inline]
 __x64_sys_access+0x33/0x40 fs/open.c:480
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22533 Comm: systemd-udevd Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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