On Thu, Jul 09, 2020 at 09:22:09AM -0700, Dave Hansen wrote: > On 7/9/20 9:07 AM, Andy Lutomirski wrote: > > On Thu, Jul 9, 2020 at 8:56 AM Dave Hansen <dave.hansen@xxxxxxxxx> wrote: > >> On 7/9/20 8:44 AM, Andersen, John wrote: > >>> Bits which are allowed to be pinned default to WP for CR0 and SMEP, > >>> SMAP, and UMIP for CR4. > >> I think it also makes sense to have FSGSBASE in this set. > >> > >> I know it hasn't been tested, but I think we should do the legwork to > >> test it. If not in this set, can we agree that it's a logical next step? > > I have no objection to pinning FSGSBASE, but is there a clear > > description of the threat model that this whole series is meant to > > address? The idea is to provide a degree of protection against an > > attacker who is able to convince a guest kernel to write something > > inappropriate to CR4, right? How realistic is this? > > If a quick search can find this: > > > https://googleprojectzero.blogspot.com/2017/05/exploiting-linux-kernel-via-packet.html > > I'd pretty confident that the guys doing actual bad things have it in > their toolbox too. Right, it's common (see my commit log in 873d50d58f67), and having this enforced by the hypervisor is WAY better since it'll block gadgets or ROP. -- Kees Cook
