linux-kernel - Re: General flags to turn things off (getrandom, pid lookup, etc)

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Date:	Fri, 25 Jul 2014 16:43:20 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Julien Tinnes <jln@...gle.com>,
	David Drysdale <drysdale@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Paolo Bonzini <pbonzini@...hat.com>,
	LSM List <linux-security-module@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Paul Moore <paul@...l-moore.com>,
	James Morris <james.l.morris@...cle.com>,
	Linux API <linux-api@...r.kernel.org>,
	Meredydd Luff <meredydd@...atehouse.org>,
	Christoph Hellwig <hch@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Kees Cook <keescook@...omium.org>,
	"Theodore Ts'o" <tytso@....edu>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	linux-crypto@...r.kernel.org
Subject: Re: General flags to turn things off (getrandom, pid lookup, etc)

On 07/25/2014 11:30 AM, Andy Lutomirski wrote:
>     - 32-bit GDT code segments [huge attack surface]
>     - 64-bit GDT code segments [probably pointless]

I presume you mean s/GDT/LDT/.

We already don't allow 64-bit LDT code segments.  Also, it is unclear to
me how 32-bit LDT segments have a huge attack surface, given that there
will realistically always be a 32-bit *GDT* segment present.

	-hpa


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