KCSAN: data-race in do_exit / exit

KCSAN: data-race in do_exit / exit_signals (3)
Status: moderation: reported on 2020/12/07 12:06
Reported-by: syzbot+74d5dfab4b8a37e04f6b@syzkaller.appspotmail.com
First crash: 57d, last: 1d19h

similar bugs (2):
Kernel	Title	Repro	Cause bisect	Fix bisect	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in do_exit / exit_signals				1	201d	201d	0/17	auto-closed as invalid on 2020/08/11 13:36
upstream	KCSAN: data-race in do_exit / exit_signals (2)				3	129d	147d	0/17	auto-closed as invalid on 2020/10/22 22:12

Sample crash report:

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

read-write to 0xffff88800e78e02c of 4 bytes by task 11160 on cpu 0:
 exit_signals+0x102/0x530 kernel/signal.c:2865
 do_exit+0x1b4/0x1690 kernel/exit.c:781
 do_group_exit+0xc8/0x170 kernel/exit.c:922
 get_signal+0xd7e/0x1470 kernel/signal.c:2773
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:811
 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+0x109/0x1a0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800e78e02c of 4 bytes by task 11157 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+0x59c/0x1690 kernel/exit.c:845
 do_group_exit+0xc8/0x170 kernel/exit.c:922
 get_signal+0xd7e/0x1470 kernel/signal.c:2773
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:811
 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+0x109/0x1a0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 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: 11157 Comm: syz-executor.2 Not tainted 5.11.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (5):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Maintainers
ci2-upstream-kcsan-gce	2021/01/23 10:51	upstream	fe75a218	52e37319	.config	log	report	info	axboe@kernel.dk, christian@brauner.io, ebiederm@xmission.com, linux-kernel@vger.kernel.org, oleg@redhat.com, pcc@google.com
ci2-upstream-kcsan-gce	2021/01/08 21:10	upstream	6279d812	c104d4a3	.config	log	report	info	axboe@kernel.dk, christian@brauner.io, ebiederm@xmission.com, linux-kernel@vger.kernel.org, oleg@redhat.com, pcc@google.com
ci2-upstream-kcsan-gce	2021/01/03 18:22	upstream	3516bd72	79264ae3	.config	log	report	info	axboe@kernel.dk, christian@brauner.io, ebiederm@xmission.com, linux-kernel@vger.kernel.org, oleg@redhat.com, pcc@google.com, tglx@linutronix.de
ci2-upstream-kcsan-gce	2020/12/24 05:21	upstream	58cf05f5	c2c1d1dd	.config	log	report	info	axboe@kernel.dk, christian@brauner.io, ebiederm@xmission.com, linux-kernel@vger.kernel.org, oleg@redhat.com, pcc@google.com
ci2-upstream-kcsan-gce	2020/11/29 05:01	upstream	67f34fa8	a0092f9d	.config	log	report	info	axboe@kernel.dk, christian@brauner.io, ebiederm@xmission.com, linux-kernel@vger.kernel.org, liuzhiqiang26@huawei.com, oleg@redhat.com