linux-kernel - Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

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Message-ID: <y0my5frsg5w.fsf@fche.csb>
Date:	Thu, 17 Jan 2013 15:33:47 -0500
From:	fche@...hat.com (Frank Ch. Eigler)
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	"Kasatkin, Dmitry" <dmitry.kasatkin@...el.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, pjones@...hat.com, hpa@...or.com,
	dhowells@...hat.com, jwboyer@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-security-module@...r.kernel.org
Subject: Re: [PATCH 2/3] binfmt_elf: Verify signature of signed elf binary

Vivek Goyal <vgoyal@...hat.com> writes:

> [...]
>> Can you please tell a bit more how this patch protect against direct
>> writing to the blocks?
>
> If you have loaded all the pages from disk and locked them in memory and
> verified the signature, then even if somebody modifies a block on disk
> it does not matter. We will not read pages from disk anymore for this
> exec(). We verified the signature of executable loaded in memory and
> in-memory copy is intact.

Does this imply dramatically increasing physical RAM pressure and load
latency, because binaries (and presumably all their shared libraries)
have to be locked & loaded?  (Else if they are paged out to
encrypted-swap, is that sufficient protection against manipulation?)

- FChE
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