From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta8.messagelabs.com (mail6.bemta8.messagelabs.com [216.82.243.55]) by kanga.kvack.org (Postfix) with ESMTP id 88C9B6B0012 for ; Sun, 3 Jul 2011 14:57:16 -0400 (EDT) Received: by bwd14 with SMTP id 14so5392372bwd.14 for ; Sun, 03 Jul 2011 11:57:14 -0700 (PDT) Date: Sun, 3 Jul 2011 22:57:09 +0400 From: Vasiliy Kulikov Subject: Re: [RFC v1] implement SL*B and stack usercopy runtime checks Message-ID: <20110703185709.GA7414@albatros> References: <20110703111028.GA2862@albatros> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Linus Torvalds Cc: kernel-hardening@lists.openwall.com, Thomas Gleixner , Ingo Molnar , "H. Peter Anvin" , x86@kernel.org, Arnd Bergmann , Christoph Lameter , Pekka Enberg , Matt Mackall , Andrew Morton , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org On Sun, Jul 03, 2011 at 11:27 -0700, Linus Torvalds wrote: > That patch is entirely insane. No way in hell will that ever get merged. Sure, this is just an RFC :) I didn't think about proposing it as a patch as is, I tried to just show how/what checks it introduces. > copy_to/from_user() is some of the most performance-critical code, and > runs a *lot*, often for fairly small structures (ie 'fstat()' etc). > > Adding random ad-hoc tests to it is entirely inappropriate. Doing so > unconditionally is insane. That's why I've asked whether it makes sense to guard it with CONFIG_XXX, defaults to =n. Some distributions might think it makes sense to enable it sacrificing some speed. Will do. > If you seriously clean it up (that at a minimum includes things like > making it configurable using some pretty helper function that just > compiles away for all the normal cases, Hm, it is not as simple as it looks at the first glance - even if the object size is known at the compile time (__compiletime_object_size), it might be a field of a structure, which crosses the slab object boundaries because of an overflow. However, if interpret constants fed to copy_*_user() as equivalent to {get,put}_user() (== worry about size argument overflow only), then it might be useful here. > if (!slab_access_ok(to, n) || !stack_access_ok(to, n)) OK :) Thanks! -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org