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 377399000BD for ; Mon, 19 Sep 2011 13:59:37 -0400 (EDT) Received: by ewy25 with SMTP id 25so1170199ewy.14 for ; Mon, 19 Sep 2011 10:59:32 -0700 (PDT) Date: Mon, 19 Sep 2011 21:58:56 +0400 From: Vasiliy Kulikov Subject: Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo Message-ID: <20110919175856.GA4282@albatros> References: <20110918170512.GA2351@albatros> <20110919144657.GA5928@albatros> <20110919155718.GB16272@albatros> <20110919161837.GA2232@albatros> <20110919173539.GA3751@albatros> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Pekka Enberg Cc: Andrew Morton , kernel-hardening@lists.openwall.com, Kees Cook , Cyrill Gorcunov , Al Viro , Christoph Lameter , Matt Mackall , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Dan Rosenberg , Theodore Tso , Alan Cox , Jesper Juhl , Linus Torvalds On Mon, Sep 19, 2011 at 20:51 +0300, Pekka Enberg wrote: > On Mon, Sep 19, 2011 at 8:35 PM, Vasiliy Kulikov wrote: > >> Yes, but there's no way for users to know where the allocations came from > >> if you mix them up with other kmalloc-128 call-sites. That way the number > >> of private files will stay private to the user, no? Doesn't that give you even > >> better protection against the infoleak? > > > > No, what it gives us is an obscurity, not a protection. I'm sure it > > highly depends on the specific situation whether an attacker is able to > > identify whether the call is from e.g. ecryptfs or from VFS. Also the > > correlation between the number in slabinfo and the real private actions > > still exists. > > How is the attacker able to identify that we kmalloc()'d from ecryptfs or > VFS based on non-root /proc/slabinfo when the slab allocator itself does > not have that sort of information if you mix up the allocations? How can you _guarantee_ that they mix? > Isn't this > much stronger protection especially if you combine that with /proc/slabinfo > restriction? I don't see any reason to change allocators if we close slabinfo. 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