linux-kernel - Re: [PATCH v2] Yama: access task

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Message-ID: <20120816165629.GA12599@redhat.com>
Date:	Thu, 16 Aug 2012 18:56:29 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Kees Cook <keescook@...omium.org>
Cc:	linux-kernel@...r.kernel.org,
	James Morris <james.l.morris@...cle.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	John Johansen <john.johansen@...onical.com>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH v2] Yama: access task_struct->comm directly

On 08/15, Kees Cook wrote:
>
> v2: update with newly added traceme report.

...

> @@ -319,12 +316,9 @@ static int yama_ptrace_traceme(struct task_struct *parent)
>  	}
>  
>  	if (rc) {
> -		char name[sizeof(current->comm)];
>  		printk_ratelimited(KERN_NOTICE
>  			"ptraceme of pid %d was attempted by: %s (pid %d)\n",
> -			current->pid,
> -			get_task_comm(name, parent),
> -			parent->pid);
> +			current->pid, parent->comm, parent->pid);

Hmm, yes. This change is even more important. This is called under
write_lock_irq(tasklist_lock), task_lock() can deadlock if we race
with another CPU doing task_lock()->interrupt->read_lock(tasklist).

Oleg.

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