linux-kernel - Re: [patch 0/5] Support for sanitization flag in low-level page allocator

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Date:	Sat, 30 May 2009 07:04:15 -0700
From:	"Larry H." <research@...reption.com>
To:	pageexec@...email.hu
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ingo Molnar <mingo@...e.hu>, Rik van Riel <riel@...hat.com>,
	linux-kernel@...r.kernel.org, Linus Torvalds <torvalds@...l.org>,
	linux-mm@...ck.org, Ingo Molnar <mingo@...hat.com>
Subject: Re: [patch 0/5] Support for sanitization flag in low-level page
	allocator

On 15:54 Sat 30 May     , pageexec@...email.hu wrote:
> On 30 May 2009 at 15:21, Peter Zijlstra wrote:
> 
> > On Sat, 2009-05-30 at 13:42 +0200, pageexec@...email.hu wrote:
> > > > Why waste time on this?
> > > 
> > > e.g., when userland executes a syscall, it 'can run kernel code'. if that kernel
> > > code (note: already exists, isn't provided by the attacker) gives unintended
> > > kernel memory back to userland, there is a problem. that problem is addressed
> > > in part by early sanitizing of freed data.
> > 
> > Right, so the whole point is to minimize the impact of actual bugs,
> > right?
> 
> correct. this approach is the manifestation of a particular philosophy
> in computer security where instead of finding all bugs, we minimize or,
> at times, eliminate their bad sideeffects. non-executable pages, ASLR,
> etc are all about this. see below why.
> 
> > So why not focus on fixing those actual bugs? Can we create tools
> > to help us find such bugs faster? We use sparse for a lot of static
> > checking, we create things like lockdep and kmemcheck to dynamically
> > find trouble.
> > 
> > Can we instead of working around a problem, fix the actual problem?
> 
> finding all use-after-free bugs is not possible, as far as i know. the
> fundamental problem is that you'd have to find bugs with arbitrary read
> sideeffects (which is just as hard a problem as finding bugs with arbitrary
> write sideeffects which you'd also have to solve). if you solve these
> problems, you'll have solved the most important bug class in computer
> security that many decades of academic/industrial/etc research failed at.

If Peter can pull this off, I'll ring the red phone and get some VC
contacts going. We will be driving Camaros in no time, and I will
finally ditch my Spyder before it puts an end to my adventure.

	Larry
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