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

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Message-ID: <54FE56C6.7000902@intel.com>
Date:	Mon, 09 Mar 2015 19:28:22 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Kees Cook <keescook@...omium.org>
CC:	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 03/09/2015 04:08 PM, Eric W. Biederman wrote:
> If the concern is to protect against root getting into the kernel the
> "trusted_kernel" snake-oil just compile out the pagemap file.  Nothing
> else is remotely interesting from a mainenance point of view.

The paper I linked to showed one example of how pagemap makes a
user->kernel exploint _easier_.  Note that the authors had another way
of actually doing the exploit when pagemap was not available, but it
required some more trouble than if pagemap was around.

I mentioned the "trusted_kernel" stuff as an aside.  It's really not the
main concern.
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