Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755536Ab2JCFiK (ORCPT ); Wed, 3 Oct 2012 01:38:10 -0400 Received: from mail-pa0-f46.google.com ([209.85.220.46]:39616 "EHLO mail-pa0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750940Ab2JCFhr (ORCPT ); Wed, 3 Oct 2012 01:37:47 -0400 Date: Tue, 2 Oct 2012 22:37:45 -0700 (PDT) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Kees Cook cc: linux-kernel@vger.kernel.org, Andrew Morton , Minchan Kim , Joe Perches , Kautuk Consul , linux-mm@kvack.org, Brad Spengler Subject: Re: [PATCH] mm: use %pK for /proc/vmallocinfo In-Reply-To: Message-ID: References: <20121002234934.GA9194@www.outflux.net> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1416 Lines: 34 On Tue, 2 Oct 2012, Kees Cook wrote: > >> In the paranoid case of sysctl kernel.kptr_restrict=2, mask the kernel > >> virtual addresses in /proc/vmallocinfo too. > >> > >> Reported-by: Brad Spengler > >> Signed-off-by: Kees Cook > > > > /proc/vmallocinfo is S_IRUSR, not S_IRUGO, so exactly what are you trying > > to protect? > > Trying to block the root user from seeing virtual memory addresses > (mode 2 of kptr_restrict). > > Documentation/sysctl/kernel.txt: > "This toggle indicates whether restrictions are placed on > exposing kernel addresses via /proc and other interfaces. When > kptr_restrict is set to (0), there are no restrictions. When > kptr_restrict is set to (1), the default, kernel pointers > printed using the %pK format specifier will be replaced with 0's > unless the user has CAP_SYSLOG. When kptr_restrict is set to > (2), kernel pointers printed using %pK will be replaced with 0's > regardless of privileges." > > Even though it's S_IRUSR, it still needs %pK for the paranoid case. > So root does echo 0 > /proc/sys/kernel/kptr_restrict first. Again: what are you trying to protect? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/