linux-kernel - Re: [PATCH 1/3] mm: vmalloc: export __vmalloc_node

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Message-ID: <ZqBHwnPW_R4lFXVK@casper.infradead.org>
Date: Wed, 24 Jul 2024 01:16:02 +0100
From: Matthew Wilcox <willy@...radead.org>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Mary Strodl <mstrodl@...edom.csh.rit.edu>,
	Christian Gmeiner <christian.gmeiner@...il.com>,
	Christoph Hellwig <hch@...radead.org>,
	Mary Strodl <mstrodl@....rit.edu>, linux-kernel@...r.kernel.org,
	urezki@...il.com, linux-mm@...ck.org, lee@...nel.org,
	andi.shyti@...nel.org, linux-i2c@...r.kernel.org,
	s.hauer@...gutronix.de
Subject: Re: [PATCH 1/3] mm: vmalloc: export __vmalloc_node_range

On Tue, Jul 23, 2024 at 05:00:43PM -0700, Andrew Morton wrote:
> On Fri, 19 Jul 2024 13:42:40 +0100 Matthew Wilcox <willy@...radead.org> wrote:
> 
> > On Fri, Jul 19, 2024 at 07:58:40AM -0400, Mary Strodl wrote:
> > > Maybe some of the stuff the driver does right now could be moved into
> > > vmalloc? In other words, we could provide a different function that
> > > allocates an executable page, copies memory into it, then marks it
> > > read-only. Would that do better to alleviate concerns?
> > 
> > No.  We are not running arbitrary x86 code.  That is a security
> > nightmare.
> 
> Sure, if such a thing were to be done we'd want it localized within the
> driver rather than offered globally.
> 
> But if there was some hack within the driver to do this, what problems
> might that cause?  What are the scenarios?

That we're running arbitrary x86 code (provided by the manufacturer)
inside the kernel where it can undermine every security guarantee we
provide?