From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41241) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Un6gF-0004hJ-Gf for qemu-devel@nongnu.org; Thu, 13 Jun 2013 08:31:08 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Un6gA-0007DT-1T for qemu-devel@nongnu.org; Thu, 13 Jun 2013 08:31:07 -0400 Received: from mail-qc0-x229.google.com ([2607:f8b0:400d:c01::229]:33525) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Un6g9-0007DP-Sd for qemu-devel@nongnu.org; Thu, 13 Jun 2013 08:31:01 -0400 Received: by mail-qc0-f169.google.com with SMTP id c10so5367679qcz.14 for ; Thu, 13 Jun 2013 05:31:01 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <51B9BB80.5080404@redhat.com> Date: Thu, 13 Jun 2013 08:30:56 -0400 From: Paolo Bonzini MIME-Version: 1.0 References: <51B96205.4010601@kamp.de> <20130613084015.GF2633@stefanha-thinkpad.redhat.com> <51B98822.1030402@kamp.de> <8761xi7016.fsf@blackfin.pond.sub.org> <87vc5iz0j8.fsf@codemonkey.ws> In-Reply-To: <87vc5iz0j8.fsf@codemonkey.ws> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] sanitize memory on system reset List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Anthony Liguori Cc: Stefan Hajnoczi , "H. Peter Anvin" , Peter Lieven , Markus Armbruster , "qemu-devel@nongnu.org" Il 13/06/2013 07:56, Anthony Liguori ha scritto: > Markus Armbruster writes: > >> Peter Lieven writes: >> >>> On 13.06.2013 10:40, Stefan Hajnoczi wrote: >>>> On Thu, Jun 13, 2013 at 08:09:09AM +0200, Peter Lieven wrote: >>>>> I was thinking if it would be a good idea to zeroize all memory >>>>> resources on system reset and >>>>> madvise dontneed them afterwards. This would avoid system reset >>>>> attacks in case the attacker >>>>> has only access to the console of a vServer but not on the physical >>>>> host and it would shrink >>>>> RSS size of the vServer siginificantly. >>>> I wonder if you'll hit weird OS installers or PXE clients that rely on >>>> stashing stuff in memory across reset. >>> One point: >>> Wouldn't a memory test which some systems do at startup break these as well? >> >> Systems that distinguish between warm and cold boot (such as PCs) >> generally run POST only on cold boot. >> >> I'm not saying triggering warm reboot and expecting memory contents to >> survive is a good idea, but it has been done. > > Doesn't kexec do a warm reboot stashing the new kernel somewhere in > memory? No, it undoes most of the hardware setup and jumps to the new kernel. It never goes through the BIOS. Paolo