KCSAN: data-race in do_exit / ptrace

KCSAN: data-race in do_exit / ptrace_stop
Status: auto-closed as invalid on 2020/10/31 14:13
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 306d, last: 305d

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in do_exit / ptrace_stop (3)				1	110d	110d	0/22	auto-closed as invalid on 2021/05/14 01:48
upstream	KCSAN: data-race in do_exit / ptrace_stop (2)				1	245d	233d	0/22	auto-closed as invalid on 2020/12/29 23:47

Sample crash report:

==================================================================
BUG: KCSAN: data-race in do_exit / ptrace_stop

write to 0xffff88811e0a7064 of 4 bytes by task 27992 on cpu 0:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 ptrace_stop+0x394/0x650 kernel/signal.c:2215
 ptrace_signal kernel/signal.c:2490 [inline]
 get_signal+0x887/0x1650 kernel/signal.c:2653
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811e0a7064 of 4 bytes by task 28000 on cpu 1:
 find_alive_thread kernel/exit.c:493 [inline]
 find_new_reaper kernel/exit.c:542 [inline]
 forget_original_parent kernel/exit.c:617 [inline]
 exit_notify kernel/exit.c:650 [inline]
 do_exit+0x7e0/0x16c0 kernel/exit.c:826
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0xe9f/0x1650 kernel/signal.c:2757
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:192
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:267
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 28000 Comm: syz-executor.1 Not tainted 5.9.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (2):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2020/09/26 14:13	upstream	7c7ec3226f5f	2d5ea0cb	.config	log	report			info
ci2-upstream-kcsan-gce	2020/09/25 14:40	upstream	171d4ff79f96	4a006f63	.config	log	report			info