diff options
| author | Sean Christopherson <seanjc@google.com> | 2023-06-13 13:30:35 -0700 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2023-07-29 11:05:31 -0400 |
| commit | 26a0652cb453c72f6aab0974bc4939e9b14f886b (patch) | |
| tree | f23de4e5d5d068a437166b6e3b7a837505989bd3 /arch/x86/kvm/vmx/vmx.c | |
| parent | 880218361c10d6dd7f99423d621112b8770fc32f (diff) | |
KVM: x86: Disallow KVM_SET_SREGS{2} if incoming CR0 is invalid
Reject KVM_SET_SREGS{2} with -EINVAL if the incoming CR0 is invalid,
e.g. due to setting bits 63:32, illegal combinations, or to a value that
isn't allowed in VMX (non-)root mode. The VMX checks in particular are
"fun" as failure to disallow Real Mode for an L2 that is configured with
unrestricted guest disabled, when KVM itself has unrestricted guest
enabled, will result in KVM forcing VM86 mode to virtual Real Mode for
L2, but then fail to unwind the related metadata when synthesizing a
nested VM-Exit back to L1 (which has unrestricted guest enabled).
Opportunistically fix a benign typo in the prototype for is_valid_cr4().
Cc: stable@vger.kernel.org
Reported-by: syzbot+5feef0b9ee9c8e9e5689@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/000000000000f316b705fdf6e2b4@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20230613203037.1968489-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/vmx/vmx.c')
| -rw-r--r-- | arch/x86/kvm/vmx/vmx.c | 28 |
1 files changed, 21 insertions, 7 deletions
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 0dd4612b0ca2..3d011d62d969 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -3047,6 +3047,15 @@ static void enter_rmode(struct kvm_vcpu *vcpu) struct vcpu_vmx *vmx = to_vmx(vcpu); struct kvm_vmx *kvm_vmx = to_kvm_vmx(vcpu->kvm); + /* + * KVM should never use VM86 to virtualize Real Mode when L2 is active, + * as using VM86 is unnecessary if unrestricted guest is enabled, and + * if unrestricted guest is disabled, VM-Enter (from L1) with CR0.PG=0 + * should VM-Fail and KVM should reject userspace attempts to stuff + * CR0.PG=0 when L2 is active. + */ + WARN_ON_ONCE(is_guest_mode(vcpu)); + vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_TR], VCPU_SREG_TR); vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_ES], VCPU_SREG_ES); vmx_get_segment(vcpu, &vmx->rmode.segs[VCPU_SREG_DS], VCPU_SREG_DS); @@ -3236,6 +3245,17 @@ void ept_save_pdptrs(struct kvm_vcpu *vcpu) #define CR3_EXITING_BITS (CPU_BASED_CR3_LOAD_EXITING | \ CPU_BASED_CR3_STORE_EXITING) +static bool vmx_is_valid_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) +{ + if (is_guest_mode(vcpu)) + return nested_guest_cr0_valid(vcpu, cr0); + + if (to_vmx(vcpu)->nested.vmxon) + return nested_host_cr0_valid(vcpu, cr0); + + return true; +} + void vmx_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0) { struct vcpu_vmx *vmx = to_vmx(vcpu); @@ -5375,18 +5395,11 @@ static int handle_set_cr0(struct kvm_vcpu *vcpu, unsigned long val) val = (val & ~vmcs12->cr0_guest_host_mask) | (vmcs12->guest_cr0 & vmcs12->cr0_guest_host_mask); - if (!nested_guest_cr0_valid(vcpu, val)) - return 1; - if (kvm_set_cr0(vcpu, val)) return 1; vmcs_writel(CR0_READ_SHADOW, orig_val); return 0; } else { - if (to_vmx(vcpu)->nested.vmxon && - !nested_host_cr0_valid(vcpu, val)) - return 1; - return kvm_set_cr0(vcpu, val); } } @@ -8214,6 +8227,7 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { .set_segment = vmx_set_segment, .get_cpl = vmx_get_cpl, .get_cs_db_l_bits = vmx_get_cs_db_l_bits, + .is_valid_cr0 = vmx_is_valid_cr0, .set_cr0 = vmx_set_cr0, .is_valid_cr4 = vmx_is_valid_cr4, .set_cr4 = vmx_set_cr4, |