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 299CB9000BD for ; Mon, 19 Sep 2011 13:36:18 -0400 (EDT) Received: by bkbzs2 with SMTP id zs2so7104474bkb.14 for ; Mon, 19 Sep 2011 10:36:16 -0700 (PDT) Date: Mon, 19 Sep 2011 21:35:39 +0400 From: Vasiliy Kulikov Subject: Re: [kernel-hardening] Re: [RFC PATCH 2/2] mm: restrict access to /proc/slabinfo Message-ID: <20110919173539.GA3751@albatros> References: <20110910164134.GA2442@albatros> <20110914192744.GC4529@outflux.net> <20110918170512.GA2351@albatros> <20110919144657.GA5928@albatros> <20110919155718.GB16272@albatros> <20110919161837.GA2232@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: 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 20:31 +0300, Pekka Enberg wrote: > On Mon, Sep 19, 2011 at 7:18 PM, Vasiliy Kulikov wrote: > >> However, if the encryptfs and infoleaks really are serious enough to > >> hide /proc/slabinfo, I think you should consider switching over to > >> kmalloc() instead of kmem_cache_alloc() to make sure nobody can > >> gain access to the information. > > > > kmalloc() is still visible in slabinfo as kmalloc-128 or so. > > 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. 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