KCSAN: data-race in __ptrace_unlink / do

KCSAN: data-race in __ptrace_unlink / do_exit (2)
Status: auto-closed as invalid on 2020/12/21 11:46
Reported-by: syzbot+48549b693a904f20c247@syzkaller.appspotmail.com
First crash: 425d, last: 388d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (3)	1	340d	340d	0/22	auto-closed as invalid on 2021/01/27 14:46
upstream	KCSAN: data-race in __ptrace_unlink / do_exit	4	461d	514d	0/22	auto-closed as invalid on 2020/09/28 07:37
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (5)	2	201d	212d	0/22	auto-closed as invalid on 2021/06/15 19:49
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (4)	1	280d	280d	0/22	auto-closed as invalid on 2021/03/28 11:03

Sample crash report:

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

write to 0xffff888063c60028 of 4 bytes by task 22119 on cpu 0:
 __ptrace_unlink+0x160/0x2f0 kernel/ptrace.c:132
 __ptrace_detach+0x1b/0x1a0 kernel/ptrace.c:528
 exit_ptrace+0x93/0x160 kernel/ptrace.c:588
 forget_original_parent kernel/exit.c:610 [inline]
 exit_notify kernel/exit.c:650 [inline]
 do_exit+0x11b3/0x15a0 kernel/exit.c:826
 do_group_exit+0xc8/0x170 kernel/exit.c:903
 get_signal+0xf9b/0x1510 kernel/signal.c:2758
 arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff888063c60028 of 4 bytes by task 22117 on cpu 1:
 ptrace_event_enabled include/linux/ptrace.h:142 [inline]
 ptrace_event include/linux/ptrace.h:157 [inline]
 do_exit+0xff/0x15a0 kernel/exit.c:747
 do_group_exit+0xc8/0x170 kernel/exit.c:903
 get_signal+0xf9b/0x1510 kernel/signal.c:2758
 arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 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: 22117 Comm: syz-executor.4 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (4):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info
ci2-upstream-kcsan-gce	2020/11/05 23:40	upstream	521b619acdc8	cba33199	.config	log	report	info
ci2-upstream-kcsan-gce	2020/10/31 02:48	upstream	f5d808567a51	18e33098	.config	log	report	info
ci2-upstream-kcsan-gce	2020/10/28 20:37	upstream	ed8780e3f2ec	f24824d3	.config	log	report	info
ci2-upstream-kcsan-gce	2020/09/30 00:41	upstream	fb0155a09b02	5abc3f1a	.config	log	report	info