linux-kernel - Re: [RFC 0/3] extend kexec_file

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Message-ID: <34243612.Gid3QHG1hd@wuerfel>
Date:	Wed, 20 Jul 2016 13:12:20 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Michael Ellerman <mpe@...erman.id.au>
Cc:	Russell King - ARM Linux <linux@...linux.org.uk>,
	Balbir Singh <bsingharora@...il.com>,
	Stewart Smith <stewart@...ux.vnet.ibm.com>, bhe@...hat.com,
	kexec@...ts.infradead.org, dyoung@...hat.com,
	Petr Tesarik <ptesarik@...e.cz>, linux-kernel@...r.kernel.org,
	AKASHI Takahiro <takahiro.akashi@...aro.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, Vivek Goyal <vgoyal@...hat.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC 0/3] extend kexec_file_load system call

On Wednesday, July 20, 2016 8:47:45 PM CEST Michael Ellerman wrote:
> At least for stdout-path, I can't really see how that would significantly help
> an attacker, but I'm all ears if anyone has ideas.

That's actually an easy one that came up before: If an attacker controls
a tty device (e.g. network console) that can be used to enter a debugger
(kdb, kgdb, xmon, ...), enabling that to be the console device
gives you a direct attack vector. The same thing will happen if you
have a piece of software that intentially gives extra rights to the
owner of the console device by treating it as "physical presence".

	Arnd