KCSAN: data-race in ptrace_check_attach / zap_other

KCSAN: data-race in ptrace_check_attach / zap_other_threads
Status: auto-closed as invalid on 2020/09/05 20:28
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 356d, last: 356d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in ptrace_check_attach / zap_other_threads (2)	1	321d	321d	0/22	auto-closed as invalid on 2020/10/10 22:50
upstream	KCSAN: data-race in ptrace_check_attach / zap_other_threads (5)	9	53d	88d	0/22	auto-closed as invalid on 2021/07/05 18:29
upstream	KCSAN: data-race in ptrace_check_attach / zap_other_threads (3)	1	262d	229d	0/22	auto-closed as invalid on 2020/12/21 11:57
upstream	KCSAN: data-race in ptrace_check_attach / zap_other_threads (4)	1	151d	151d	0/22	auto-closed as invalid on 2021/03/30 13:55

Sample crash report:

==================================================================
BUG: KCSAN: data-race in ptrace_check_attach / zap_other_threads

write to 0xffff88809cc7f488 of 8 bytes by task 13227 on cpu 0:
 task_clear_jobctl_pending kernel/signal.c:344 [inline]
 zap_other_threads+0x98/0x1e0 kernel/signal.c:1355
 do_group_exit+0x146/0x180 kernel/exit.c:898
 __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+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809cc7f488 of 8 bytes by task 13229 on cpu 1:
 ptrace_freeze_traced kernel/ptrace.c:178 [inline]
 ptrace_check_attach+0xd8/0x220 kernel/ptrace.c:247
 __do_sys_ptrace kernel/ptrace.c:1272 [inline]
 __se_sys_ptrace+0xdb/0x2d0 kernel/ptrace.c:1242
 __x64_sys_ptrace+0x51/0x60 kernel/ptrace.c:1242
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13229 Comm: syz-executor.0 Not tainted 5.8.0-rc7-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	2020/08/01 20:20	upstream	d52daa8620c6	8df85ed9	.config	log	report