KCSAN: data-race in detach_pid / proc_pid

KCSAN: data-race in detach_pid / proc_pid_status (3)
Status: auto-closed as invalid on 2021/05/23 14:20
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 102d, last: 102d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in detach_pid / proc_pid_status (2)				1	209d	209d	0/22	auto-closed as invalid on 2021/02/05 23:49
upstream	KCSAN: data-race in detach_pid / proc_pid_status				1	279d	279d	0/22	auto-closed as invalid on 2020/11/28 03:16

Sample crash report:

==================================================================
BUG: KCSAN: data-race in detach_pid / proc_pid_status

write to 0xffff888137d755d8 of 8 bytes by task 1025 on cpu 0:
 __change_pid kernel/pid.c:347 [inline]
 detach_pid+0xd7/0x160 kernel/pid.c:358
 __unhash_process kernel/exit.c:75 [inline]
 __exit_signal kernel/exit.c:148 [inline]
 release_task+0x6d8/0xbe0 kernel/exit.c:199
 wait_task_zombie kernel/exit.c:1107 [inline]
 wait_consider_task+0x10ce/0x19e0 kernel/exit.c:1334
 do_wait_thread kernel/exit.c:1397 [inline]
 do_wait+0x1b1/0x4a0 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+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888137d755d8 of 8 bytes by task 1024 on cpu 1:
 pid_alive include/linux/sched.h:1442 [inline]
 task_state fs/proc/array.c:164 [inline]
 proc_pid_status+0xac/0x13c0 fs/proc/array.c:443
 proc_single_show+0x84/0x100 fs/proc/base.c:774
 seq_read_iter+0x2ef/0x910 fs/seq_file.c:227
 seq_read+0x221/0x260 fs/seq_file.c:159
 vfs_read+0x154/0x5d0 fs/read_write.c:494
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x34/0x50 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 1024 Comm: systemd-journal Tainted: G        W         5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2021/04/18 14:10	upstream	c98ff1d013d2	7e2b734b	.config	log	report			info	KCSAN: data-race in detach_pid / proc_pid_status