syzbot

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BUG: KCSAN: data-race in do_exit / ptrace_stop

write to 0xffff88810906302c of 4 bytes by task 15607 on cpu 0:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 ptrace_stop+0x392/0x650 kernel/signal.c:2216
 ptrace_do_notify kernel/signal.c:2269 [inline]
 ptrace_notify+0x109/0x160 kernel/signal.c:2279
 ptrace_report_syscall include/linux/tracehook.h:66 [inline]
 tracehook_report_syscall_entry include/linux/tracehook.h:105 [inline]
 arch_syscall_enter_tracehook include/linux/entry-common.h:98 [inline]
 syscall_trace_enter+0x87/0x2b0 kernel/entry/common.c:60
 __syscall_enter_from_user_work kernel/entry/common.c:89 [inline]
 syscall_enter_from_user_mode+0x1c/0x20 kernel/entry/common.c:107
 do_syscall_64+0x11/0x80 arch/x86/entry/common.c:41
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810906302c of 4 bytes by task 15605 on cpu 1:
 find_alive_thread kernel/exit.c:511 [inline]
 find_new_reaper kernel/exit.c:560 [inline]
 forget_original_parent kernel/exit.c:635 [inline]
 exit_notify kernel/exit.c:668 [inline]
 do_exit+0x570/0x15e0 kernel/exit.c:845
 do_group_exit+0xce/0x180 kernel/exit.c:922
 get_signal+0xf93/0x1510 kernel/signal.c:2781
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x11a/0x1b0 kernel/entry/common.c:208
 irqentry_exit_to_user_mode+0x5/0x20 kernel/entry/common.c:314
 irqentry_exit+0xe/0x40 kernel/entry/common.c:405
 asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:577

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 15605 Comm: syz-executor.4 Not tainted 5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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