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Peter Anvin" , Shuah Khan , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, Yosry Ahmed Cc: Jim Mattson Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Cache g_pat from vmcb12 in vmcb_save_area_cached to avoid TOCTTOU issues, and add a validity check so that when nested paging is enabled for vmcb12, an invalid g_pat at emulated VMRUN causes an immediate VMEXIT with exit code VMEXIT_INVALID, as specified in the APM, volume 2: "Nested Paging and VMRUN/VMEXIT." Fixes: 3d6368ef580a ("KVM: SVM: Add VMRUN handler") Signed-off-by: Jim Mattson Reviewed-by: Yosry Ahmed --- arch/x86/kvm/svm/nested.c | 17 +++++++++++++---- arch/x86/kvm/svm/svm.h | 1 + 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c index b72a1f3c4144..91b35adb83f8 100644 --- a/arch/x86/kvm/svm/nested.c +++ b/arch/x86/kvm/svm/nested.c @@ -426,7 +426,8 @@ static bool nested_vmcb_check_controls(struct kvm_vcpu = *vcpu, =20 /* Common checks that apply to both L1 and L2 state. */ static bool nested_vmcb_check_save(struct kvm_vcpu *vcpu, - struct vmcb_save_area_cached *save) + struct vmcb_save_area_cached *save, + bool check_gpat) { if (CC(!(save->efer & EFER_SVME))) return false; @@ -462,6 +463,9 @@ static bool nested_vmcb_check_save(struct kvm_vcpu *vcp= u, if (CC(!kvm_valid_efer(vcpu, save->efer))) return false; =20 + if (check_gpat && CC(!kvm_pat_valid(save->g_pat))) + return false; + return true; } =20 @@ -573,6 +577,7 @@ static void __nested_copy_vmcb_save_to_cache(struct vmc= b_save_area_cached *to, =20 to->rax =3D from->rax; to->cr2 =3D from->cr2; + to->g_pat =3D from->g_pat; =20 svm_copy_lbrs(to, from); } @@ -1036,7 +1041,8 @@ int enter_svm_guest_mode(struct kvm_vcpu *vcpu, u64 v= mcb12_gpa, bool from_vmrun) =20 enter_guest_mode(vcpu); =20 - if (!nested_vmcb_check_save(vcpu, &svm->nested.save) || + if (!nested_vmcb_check_save(vcpu, &svm->nested.save, + nested_npt_enabled(svm)) || !nested_vmcb_check_controls(vcpu, &svm->nested.ctl, svm->vmcb01.ptr->save.cr0)) return -EINVAL; @@ -2006,13 +2012,16 @@ static int svm_set_nested_state(struct kvm_vcpu *vc= pu, =20 /* * Validate host state saved from before VMRUN (see - * nested_svm_check_permissions). + * nested_svm_check_permissions). Note that the g_pat field is not + * validated, because (a) it may have been clobbered by SMM before + * KVM_GET_NESTED_STATE, and (b) it is not loaded at emulated + * #VMEXIT. */ __nested_copy_vmcb_save_to_cache(&save_cached, save); if (!(save->cr0 & X86_CR0_PG) || !(save->cr0 & X86_CR0_PE) || (save->rflags & X86_EFLAGS_VM) || - !nested_vmcb_check_save(vcpu, &save_cached)) + !nested_vmcb_check_save(vcpu, &save_cached, false)) goto out_free; =20 =20 diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h index 9850ed01e16e..a49c48459e0b 100644 --- a/arch/x86/kvm/svm/svm.h +++ b/arch/x86/kvm/svm/svm.h @@ -161,6 +161,7 @@ struct vmcb_save_area_cached { u64 isst_addr; u64 rax; u64 cr2; + u64 g_pat; u64 dbgctl; u64 br_from; u64 br_to; --=20 2.53.0.239.g8d8fc8a987-goog