KCSAN: data-race in __ptrace_unlink / do

KCSAN: data-race in __ptrace_unlink / do_exit (4)
Status: auto-closed as invalid on 2021/03/28 11:03
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 246d, last: 246d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (3)	1	306d	306d	0/22	auto-closed as invalid on 2021/01/27 14:46
upstream	KCSAN: data-race in __ptrace_unlink / do_exit	4	427d	480d	0/22	auto-closed as invalid on 2020/09/28 07:37
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (2)	4	353d	322d	0/22	auto-closed as invalid on 2020/12/21 11:46
upstream	KCSAN: data-race in __ptrace_unlink / do_exit (5)	2	166d	177d	0/22	auto-closed as invalid on 2021/06/15 19:49

Sample crash report:

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

write to 0xffff88802f662030 of 4 bytes by task 23875 on cpu 0:
 __ptrace_unlink+0x162/0x300 kernel/ptrace.c:132
 __ptrace_detach+0x1b/0x1a0 kernel/ptrace.c:522
 exit_ptrace+0x93/0x160 kernel/ptrace.c:582
 forget_original_parent kernel/exit.c:628 [inline]
 exit_notify kernel/exit.c:668 [inline]
 do_exit+0x1279/0x1690 kernel/exit.c:845
 do_group_exit+0xce/0x180 kernel/exit.c:922
 get_signal+0xdce/0x14e0 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+0x11a/0x1b0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:294
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88802f662030 of 4 bytes by task 23873 on cpu 1:
 ptrace_event_enabled include/linux/ptrace.h:142 [inline]
 ptrace_event include/linux/ptrace.h:157 [inline]
 do_exit+0x101/0x1690 kernel/exit.c:765
 do_group_exit+0xce/0x180 kernel/exit.c:922
 get_signal+0xdce/0x14e0 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+0x11a/0x1b0 kernel/entry/common.c:201
 __syscall_exit_to_user_mode_work kernel/entry/common.c:283 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:294
 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: 23873 Comm: syz-executor.3 Not tainted 5.11.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2021/02/21 11:03	upstream	e767b3530acb	3e5ed8b4	.config	log	report			info	KCSAN: data-race in __ptrace_unlink / do_exit