From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jeremy Fitzhardinge Subject: Re: [PATCH] paravirt.h Date: Tue, 22 Aug 2006 07:59:55 -0700 Message-ID: <44EB1BEB.60202@goop.org> References: <1155202505.18420.5.camel@localhost.localdomain> <44DB7596.6010503@goop.org> <1156254965.27114.17.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1156254965.27114.17.camel@localhost.localdomain> Sender: linux-kernel-owner@vger.kernel.org To: Alan Cox Cc: Rusty Russell , Andi Kleen , Andrew Morton , virtualization , Linux Kernel Mailing List , Chris Wright List-Id: virtualization@lists.linuxfoundation.org Alan Cox wrote: > It would be nice not to export it at all or to protect it, paravirt_ops > is a rootkit authors dream ticket. I'm opposed to paravirt_ops until it > is properly protected, its an unpleasantly large security target if not. > Do you have an example of an attack which would become significantly easier with pv_ops in use? I agree it might make a juicy target, but surely it is just a matter of degree given that any attacker who can get to pv_ops can do pretty much anything else. > It would be a lot safer if we could have the struct paravirt_ops in > protected read-only const memory space, set it up in the core kernel > early on in boot when we play "guess todays hypervisor" and then make > sure it stays in read only (even to kernel) space. > Yes, I'd thought about doing something like that, but as Arjan pointed out, nothing is actually read-only in the kernel when using a 2M mapping. It's also ameliorated by the fact that some of the entrypoints are never used at runtime, because the code has been patched inline (but I don't think it would ever be desirable to patch every entrypoint, since some are just not worth the effort, complexity or obfuscation which result from patching). J