On Thu, Aug 14, 2014 at 12:01 AM, Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote: > From: David Matlack <dmatlack@xxxxxxxxxx> > > The following events can lead to an incorrect KVM_EXIT_MMIO bubbling > up to userspace: > > (1) Guest accesses gpa X without a memory slot. The gfn is cached in > struct kvm_vcpu_arch (mmio_gfn). On Intel EPT-enabled hosts, KVM sets > the SPTE write-execute-noread so that future accesses cause > EPT_MISCONFIGs. > > (2) Host userspace creates a memory slot via KVM_SET_USER_MEMORY_REGION > covering the page just accessed. > > (3) Guest attempts to read or write to gpa X again. On Intel, this > generates an EPT_MISCONFIG. The memory slot generation number that > was incremented in (2) would normally take care of this but we fast > path mmio faults through quickly_check_mmio_pf(), which only checks > the per-vcpu mmio cache. Since we hit the cache, KVM passes a > KVM_EXIT_MMIO up to userspace. > > This patch fixes the issue by using the memslot generation number > to validate the mmio cache. > > [ xiaoguangrong: adjust the code to make it simpler for stable-tree fix. ] The adjustments look good. Thanks! -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
