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BUG: KCSAN: data-race in __change_pid / __task_pid_nr_ns

write to 0xffff888125306600 of 8 bytes by task 8275 on cpu 1:
 __change_pid+0x120/0x1f0 kernel/pid.c:341
 detach_pid+0x29/0x40 kernel/pid.c:352
 __unhash_process kernel/exit.c:75 [inline]
 __exit_signal kernel/exit.c:157 [inline]
 release_task+0x760/0xc60 kernel/exit.c:207
 wait_task_zombie kernel/exit.c:1080 [inline]
 wait_consider_task+0x1b3f/0x1c60 kernel/exit.c:1307
 do_wait_thread kernel/exit.c:1370 [inline]
 do_wait+0x1c9/0x4c0 kernel/exit.c:1441
 kernel_wait4+0x156/0x240 kernel/exit.c:1613
 __do_sys_wait4+0xea/0x100 kernel/exit.c:1625
 __se_sys_wait4 kernel/exit.c:1621 [inline]
 __x64_sys_wait4+0x5e/0x80 kernel/exit.c:1621
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888125306600 of 8 bytes by task 9159 on cpu 0:
 pid_alive include/linux/sched.h:1356 [inline]
 __task_pid_nr_ns+0x57/0x1e0 kernel/pid.c:475
 perf_event_pid_type+0x61/0xb0 kernel/events/core.c:1330
 perf_event_pid kernel/events/core.c:1339 [inline]
 perf_event_switch_output+0x2ae/0x300 kernel/events/core.c:8019
 perf_iterate_sb_cpu kernel/events/core.c:7058 [inline]
 perf_iterate_sb+0x3fe/0x530 kernel/events/core.c:7088
 perf_event_switch kernel/events/core.c:8065 [inline]
 __perf_event_task_sched_in+0x1bd/0x390 kernel/events/core.c:3628
 perf_event_task_sched_in include/linux/perf_event.h:1179 [inline]
 finish_task_switch+0x104/0x260 kernel/sched/core.c:3222
 context_switch kernel/sched/core.c:3388 [inline]
 __schedule+0x30e/0x690 kernel/sched/core.c:4081
 preempt_schedule_irq+0x57/0x90 kernel/sched/core.c:4338
 restore_regs_and_return_to_kernel+0x0/0x25
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:752 [inline]
 kfree+0xd1/0x180 mm/slab.c:3758
 tomoyo_realpath_from_path+0x155/0x4c0 security/tomoyo/realpath.c:319
 tomoyo_get_realpath security/tomoyo/file.c:151 [inline]
 tomoyo_check_open_permission+0x201/0x320 security/tomoyo/file.c:771
 tomoyo_file_open security/tomoyo/tomoyo.c:319 [inline]
 tomoyo_file_open+0x75/0x90 security/tomoyo/tomoyo.c:314
 security_file_open+0x69/0x210 security/security.c:1497
 do_dentry_open+0x211/0x970 fs/open.c:784
 vfs_open+0x62/0x80 fs/open.c:914
 do_last fs/namei.c:3420 [inline]
 path_openat+0xf9f/0x3580 fs/namei.c:3537
 do_filp_open+0x11e/0x1b0 fs/namei.c:3567
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 9159 Comm: blkid Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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