linux-kernel - Re: [PATCH 8/9] ptrace: Use siglock instead of tasklist_lock in ptrace_check

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Date:   Wed, 27 Apr 2022 17:20:18 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     "Eric W. Biederman" <ebiederm@...ssion.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 8/9] ptrace: Use siglock instead of tasklist_lock in
 ptrace_check_attach

On 04/26, Eric W. Biederman wrote:
>
> +	if (lock_task_sighand(child, &flags)) {
> +		if (child->ptrace && child->parent == current) {
> +			WARN_ON(READ_ONCE(child->__state) == __TASK_TRACED);
> +			/*
> +			 * child->sighand can't be NULL, release_task()
> +			 * does ptrace_unlink() before __exit_signal().
> +			 */
> +			if (ignore_state || ptrace_freeze_traced(child))
> +				ret = 0;

The comment above is no longer relevant, it should be removed.

Oleg.