syzbot

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BUG: KCSAN: data-race in dput / select_collect

write to 0xffff8880b4a8d900 of 4 bytes by task 8819 on cpu 1:
 d_lru_del fs/dcache.c:410 [inline]
 select_collect+0xaf/0x2b0 fs/dcache.c:1505
 d_walk+0x285/0x4d0 fs/dcache.c:1326
 shrink_dcache_parent+0x85/0x3f0 fs/dcache.c:1565
 d_invalidate+0x6e/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:3309
 release_task+0xa97/0xb90 kernel/exit.c:220
 wait_task_zombie kernel/exit.c:1088 [inline]
 wait_consider_task+0x104f/0x18c0 kernel/exit.c:1315
 do_wait_thread kernel/exit.c:1378 [inline]
 do_wait+0x1b1/0x4e0 kernel/exit.c:1449
 kernel_wait4+0x13c/0x1a0 kernel/exit.c:1621
 __do_sys_wait4 kernel/exit.c:1633 [inline]
 __se_sys_wait4 kernel/exit.c:1629 [inline]
 __x64_sys_wait4+0x7a/0x100 kernel/exit.c:1629
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b4a8d900 of 4 bytes by task 25081 on cpu 0:
 fast_dput fs/dcache.c:746 [inline]
 dput+0x2f/0x420 fs/dcache.c:865
 proc_invalidate_siblings_dcache+0x1eb/0x2d0 fs/proc/inode.c:151
 proc_flush_pid+0x16/0x20 fs/proc/base.c:3309
 release_task+0xa97/0xb90 kernel/exit.c:220
 exit_notify kernel/exit.c:680 [inline]
 do_exit+0x1140/0x16e0 kernel/exit.c:826
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0x106d/0x1650 kernel/signal.c:2743
 do_signal+0x25/0x270 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:235 [inline]
 __prepare_exit_to_usermode+0x127/0x230 arch/x86/entry/common.c:269
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:352
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 25081 Comm: syz-executor.2 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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