From: Andrew Cooper Date: Tue, 14 Mar 2017 11:40:36 +0000 (+0100) Subject: x86/vmx: Don't leak host syscall MSR state into HVM guests X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=6289c3b7c4756bca341ba59e4e246706040f7919;p=people%2Froyger%2Fxen.git x86/vmx: Don't leak host syscall MSR state into HVM guests hvm_hw_cpu->msr_flags is in fact the VMX dirty bitmap of MSRs needing to be restored when switching into guest context. It should never have been part of the migration state to start with, and Xen must not make any decisions based on the value seen during restore. Identify it as obsolete in the header files, consistently save it as zero and ignore it on restore. The MSRs must be considered dirty during VMCS creation to cause the proper defaults of 0 to be visible to the guest. Signed-off-by: Andrew Cooper Reviewed-by: Jan Beulich Reviewed-by: Kevin Tian master commit: 2f1add6e1c8789d979daaafa3d80ddc1bc375783 master date: 2017-02-21 11:06:39 +0000 --- diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c index 37bd6c4b18..8edc846a2e 100644 --- a/xen/arch/x86/hvm/svm/svm.c +++ b/xen/arch/x86/hvm/svm/svm.c @@ -353,7 +353,7 @@ static void svm_save_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data) data->msr_cstar = vmcb->cstar; data->msr_syscall_mask = vmcb->sfmask; data->msr_efer = v->arch.hvm_vcpu.guest_efer; - data->msr_flags = -1ULL; + data->msr_flags = 0; } diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c index 7879556568..4646ecc28d 100644 --- a/xen/arch/x86/hvm/vmx/vmcs.c +++ b/xen/arch/x86/hvm/vmx/vmcs.c @@ -1104,6 +1104,9 @@ static int construct_vmcs(struct vcpu *v) vmx_disable_intercept_for_msr(v, MSR_IA32_BNDCFGS, MSR_TYPE_R | MSR_TYPE_W); } + /* All guest MSR state is dirty. */ + v->arch.hvm_vmx.msr_state.flags = ((1u << VMX_MSR_COUNT) - 1); + /* I/O access bitmap. */ __vmwrite(IO_BITMAP_A, __pa(d->arch.hvm_domain.io_bitmap)); __vmwrite(IO_BITMAP_B, __pa(d->arch.hvm_domain.io_bitmap) + PAGE_SIZE); diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c index 8949ad6e3c..9a42e2e533 100644 --- a/xen/arch/x86/hvm/vmx/vmx.c +++ b/xen/arch/x86/hvm/vmx/vmx.c @@ -739,13 +739,12 @@ static int vmx_vmcs_restore(struct vcpu *v, struct hvm_hw_cpu *c) static void vmx_save_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data) { struct vmx_msr_state *guest_state = &v->arch.hvm_vmx.msr_state; - unsigned long guest_flags = guest_state->flags; data->shadow_gs = v->arch.hvm_vmx.shadow_gs; data->msr_cstar = v->arch.hvm_vmx.cstar; /* save msrs */ - data->msr_flags = guest_flags; + data->msr_flags = 0; data->msr_lstar = guest_state->msrs[VMX_INDEX_MSR_LSTAR]; data->msr_star = guest_state->msrs[VMX_INDEX_MSR_STAR]; data->msr_syscall_mask = guest_state->msrs[VMX_INDEX_MSR_SYSCALL_MASK]; @@ -756,7 +755,7 @@ static void vmx_load_cpu_state(struct vcpu *v, struct hvm_hw_cpu *data) struct vmx_msr_state *guest_state = &v->arch.hvm_vmx.msr_state; /* restore msrs */ - guest_state->flags = data->msr_flags & 7; + guest_state->flags = ((1u << VMX_MSR_COUNT) - 1); guest_state->msrs[VMX_INDEX_MSR_LSTAR] = data->msr_lstar; guest_state->msrs[VMX_INDEX_MSR_STAR] = data->msr_star; guest_state->msrs[VMX_INDEX_MSR_SYSCALL_MASK] = data->msr_syscall_mask; diff --git a/xen/include/public/arch-x86/hvm/save.h b/xen/include/public/arch-x86/hvm/save.h index 8d73b51f06..419a3b23d4 100644 --- a/xen/include/public/arch-x86/hvm/save.h +++ b/xen/include/public/arch-x86/hvm/save.h @@ -135,7 +135,7 @@ struct hvm_hw_cpu { uint64_t shadow_gs; /* msr content saved/restored. */ - uint64_t msr_flags; + uint64_t msr_flags; /* Obsolete, ignored. */ uint64_t msr_lstar; uint64_t msr_star; uint64_t msr_cstar; @@ -249,7 +249,7 @@ struct hvm_hw_cpu_compat { uint64_t shadow_gs; /* msr content saved/restored. */ - uint64_t msr_flags; + uint64_t msr_flags; /* Obsolete, ignored. */ uint64_t msr_lstar; uint64_t msr_star; uint64_t msr_cstar;