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Message-ID: <87o80m7afv.fsf@email.froward.int.ebiederm.org>
Date: Wed, 27 Apr 2022 11:33:40 -0500
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: Oleg Nesterov <oleg@...hat.com>
Cc: linux-kernel@...r.kernel.org, rjw@...ysocki.net, mingo@...nel.org,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, mgorman@...e.de, bigeasy@...utronix.de,
Will Deacon <will@...nel.org>, tj@...nel.org,
linux-pm@...r.kernel.org, Peter Zijlstra <peterz@...radead.org>,
Richard Weinberger <richard@....at>,
Anton Ivanov <anton.ivanov@...bridgegreys.com>,
Johannes Berg <johannes@...solutions.net>,
linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
Max Filippov <jcmvbkbc@...il.com>,
inux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
Jann Horn <jannh@...gle.com>
Subject: Re: [PATCH 9/9] ptrace: Don't change __state
Oleg Nesterov <oleg@...hat.com> writes:
> On 04/26, Eric W. Biederman wrote:
>>
>> @@ -253,7 +252,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state)
>> */
>> if (lock_task_sighand(child, &flags)) {
>> if (child->ptrace && child->parent == current) {
>> - WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
>> + WARN_ON(child->jobctl & JOBCTL_DELAY_WAKEKILL);
>
> This WARN_ON() doesn't look right.
>
> It is possible that this child was traced by another task and PTRACE_DETACH'ed,
> but it didn't clear DELAY_WAKEKILL.
That would be a bug. That would mean that PTRACE_DETACHED process can
not be SIGKILL'd.
> If the new debugger attaches and calls ptrace() before the child takes siglock
> ptrace_freeze_traced() will fail, but we can hit this WARN_ON().
Eric
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