Wind River Support Network

Description

In the Linux kernel, the following vulnerability has been resolved:  KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE  When installing an emulated MMIO SPTE, do so *after* dropping/zapping the existing SPTE (if it's shadow-present).  While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a _guest_ write, it failed to account for writes to guest memory that are outside the scope of KVM.  E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE.    ------------[ cut here ]------------   is_shadow_present_pte(*sptep)   WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292   Modules linked in: kvm_intel kvm irqbypass   CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT   Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015   RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm]   Call Trace:    <TASK>    mmu_set_spte+0x237/0x440 [kvm]    ept_page_fault+0x535/0x7f0 [kvm]    kvm_mmu_do_page_fault+0xee/0x1f0 [kvm]    kvm_mmu_page_fault+0x8d/0x620 [kvm]    vmx_handle_exit+0x18c/0x5a0 [kvm_intel]    kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm]    kvm_vcpu_ioctl+0x2d5/0x980 [kvm]    __x64_sys_ioctl+0x8a/0xd0    do_syscall_64+0xb5/0x730    entry_SYSCALL_64_after_hwframe+0x4b/0x53   RIP: 0033:0x47fa3f    </TASK>   ---[ end trace 0000000000000000 ]---