From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail6.bemta7.messagelabs.com (mail6.bemta7.messagelabs.com [216.82.255.55]) by kanga.kvack.org (Postfix) with ESMTP id 6A7B89000BD for ; Mon, 19 Sep 2011 13:52:01 -0400 (EDT) Received: by vws7 with SMTP id 7so9974442vws.35 for ; Mon, 19 Sep 2011 10:51:59 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <20110919173539.GA3751@albatros> References: <20110910164134.GA2442@albatros> <20110914192744.GC4529@outflux.net> <20110918170512.GA2351@albatros> <20110919144657.GA5928@albatros> <20110919155718.GB16272@albatros> <20110919161837.GA2232@albatros> <20110919173539.GA3751@albatros> Date: Mon, 19 Sep 2011 20:51:59 +0300 Message-ID: Subject: Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo From: Pekka Enberg Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-mm@kvack.org List-ID: To: Vasiliy Kulikov 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 8:35 PM, Vasiliy Kulikov wrot= e: >> Yes, but there's no way for users to know where the allocations came fro= m >> if you mix them up with other kmalloc-128 call-sites. That way the numbe= r >> of private files will stay private to the user, no? Doesn't that give yo= u even >> better protection against the infoleak? > > No, what it gives us is an obscurity, not a protection. =A0I'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. =A0Also 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? Isn't this much stronger protection especially if you combine that with /proc/slabinfo restriction? Pekka -- 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