linux-kernel - Re: [RFC][PATCH 1/2] fs proc: make pagemap a privileged interface

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Message-ID: <CAGXu5jLC3u2DNRPRrDONm=iQ7y4-bLs4+J1VTt6_NqAkrmrkTw@mail.gmail.com>
Date:	Mon, 9 Mar 2015 17:03:40 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Dave Hansen <dave@...1.net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Theodore Ts'o" <tytso@....edu>, Oleg Nesterov <oleg@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>
Subject: Re: [RFC][PATCH 1/2] fs proc: make pagemap a privileged interface

On Mon, Mar 9, 2015 at 4:43 PM, Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
> A 1 to 1 blinding function like integer multiplication mudulo 2^32 by an
> appropriate random number ought to keep from revealing page numbers or
> page ajacencies while not requiring any changes in userspace.
>
> That way the revealed pfn and the physcial pfn would be different but
> you could still use pagemap for it's intended purpose.

If this could be done in a way where it was sufficiently hard to
expose the random number, we should absolutely do this. And this could
be done for socket handles in INET_DIAG too. We have a lot of these
kinds of "handle" leaks where the handle's can be regarded as private
information leakage.

-Kees


-- 
Kees Cook
Chrome OS Security
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