linux-kernel - Re: [Patch 14/21] Create ELF header

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Message-ID: <20101214162406.GG11400@redhat.com>
Date:	Tue, 14 Dec 2010 17:24:06 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	"Suzuki K. Poulose" <suzuki@...ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Christoph Hellwig <hch@....de>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Roland McGrath <roland@...hat.com>,
	Amerigo Wang <amwang@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Patch 14/21] Create ELF header

On 12/14, Suzuki K. Poulose wrote:
>
> +static void get_elfhdr_size(struct core_proc *cp)
> +{
> +	struct vm_area_struct *gate_vma;
> +	int segs;
> +
> +	segs = cp->task->mm->map_count;

But this is unsafe. What if cp->task was stopped when
open_gencore() was called? In this case it can be killed/dead.

cp->task->mm can be NULL. In fact, cp->task can point to nothing.

Any usage of cp->task is not safe, afaics.

Oleg.

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