KCSAN: data-race in do_exit / exit

KCSAN: data-race in do_exit / exit_signals (2)
Status: auto-closed as invalid on 2020/10/22 22:12
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 423d, last: 405d

similar bugs (3):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in do_exit / exit_signals (3)	7	264d	325d	0/22	auto-closed as invalid on 2021/03/13 07:46
upstream	KCSAN: data-race in do_exit / exit_signals	1	478d	478d	0/22	auto-closed as invalid on 2020/08/11 13:36
upstream	KCSAN: data-race in do_exit / exit_signals (4)	4	165d	202d	0/22	auto-closed as invalid on 2021/06/20 08:01

Sample crash report:

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

write to 0xffff88811e28b024 of 4 bytes by task 17593 on cpu 0:
 exit_signals+0x124/0x580 kernel/signal.c:2845
 do_exit+0x19a/0x16c0 kernel/exit.c:762
 do_group_exit+0x17a/0x180 kernel/exit.c:903
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:914
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:912
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811e28b024 of 4 bytes by task 17615 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:159 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:265
 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: 17615 Comm: syz-executor.1 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info
ci2-upstream-kcsan-gce	2020/09/17 22:03	upstream	4cbffc461ec9	8247808b	.config	log	report	info
ci2-upstream-kcsan-gce	2020/09/16 23:34	upstream	5925fa68fe82	77507d02	.config	log	report	info
ci2-upstream-kcsan-gce	2020/08/31 04:19	upstream	dcc5c6f013d8	d5a3ae1f	.config	log	report