linux-kernel - Re: [PATCH 31/31] x86, pkeys: execute-only support

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Message-ID: <568EE5D3.1080006@sr71.net>
Date:	Thu, 7 Jan 2016 14:25:23 -0800
From:	Dave Hansen <dave@...1.net>
To:	Kees Cook <keescook@...gle.com>
Cc:	LKML <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>,
	"x86@...nel.org" <x86@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH 31/31] x86, pkeys: execute-only support

On 01/07/2016 01:02 PM, Kees Cook wrote:
>> > I haven't found any userspace that does this today.  With this
>> > facility in place, we expect userspace to move to use it
>> > eventually.
> And the magic benefit here is that linker/loaders can switch to just
> PROT_EXEC without PROT_READ, and everything that doesn't support this
> protection will silently include PROT_READ, so no runtime detection by
> the loader is needed.

Yep, completely agree.

I'll update the description.

>> > The security provided by this approach is not comprehensive.  The
> Perhaps specifically mention what it does provide, which would be
> protection against leaking executable memory contents, as generally
> done by attackers who are attempting to find ROP gadgets on the fly.

Good point.