KVM: x86: Check non-canonical addresses upon WRMSR

Upon WRMSR, the CPU should inject #GP if a non-canonical value (address) is
written to certain MSRs. The behavior is "almost" identical for AMD and Intel
(ignoring MSRs that are not implemented in either architecture since they would
anyhow #GP). However, IA32_SYSENTER_ESP and IA32_SYSENTER_EIP cause #GP if
non-canonical address is written on Intel but not on AMD (which ignores the top
32-bits).

Accordingly, this patch injects a #GP on the MSRs which behave identically on
Intel and AMD.  To eliminate the differences between the architecutres, the
value which is written to IA32_SYSENTER_ESP and IA32_SYSENTER_EIP is turned to
canonical value before writing instead of injecting a #GP.

Some references from Intel and AMD manuals:

According to Intel SDM description of WRMSR instruction #GP is expected on
WRMSR "If the source register contains a non-canonical address and ECX
specifies one of the following MSRs: IA32_DS_AREA, IA32_FS_BASE, IA32_GS_BASE,
IA32_KERNEL_GS_BASE, IA32_LSTAR, IA32_SYSENTER_EIP, IA32_SYSENTER_ESP."

According to AMD manual instruction manual:
LSTAR/CSTAR (SYSCALL): "The WRMSR instruction loads the target RIP into the
LSTAR and CSTAR registers.  If an RIP written by WRMSR is not in canonical
form, a general-protection exception (#GP) occurs."
IA32_GS_BASE and IA32_FS_BASE (WRFSBASE/WRGSBASE): "The address written to the
base field must be in canonical form or a #GP fault will occur."
IA32_KERNEL_GS_BASE (SWAPGS): "The address stored in the KernelGSbase MSR must
be in canonical form."

This patch fixes CVE-2014-3610.

Cc: stable@vger.kernel.org
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
{
	struct vcpu_svm *svm = to_svm(vcpu);

	switch (ecx) {
	case MSR_IA32_TSC: {
		*data = svm->vmcb->control.tsc_offset +
			svm_scale_tsc(vcpu, native_read_tsc());

		break;
	}
	case MSR_STAR:
		*data = svm->vmcb->save.star;
		break;
#ifdef CONFIG_X86_64
	case MSR_LSTAR:
		*data = svm->vmcb->save.lstar;
		break;
	case MSR_CSTAR:
		*data = svm->vmcb->save.cstar;
		break;
	case MSR_KERNEL_GS_BASE:
		*data = svm->vmcb->save.kernel_gs_base;
		break;
	case MSR_SYSCALL_MASK:
		*data = svm->vmcb->save.sfmask;
		break;
#endif
	case MSR_IA32_SYSENTER_CS:
		*data = svm->vmcb->save.sysenter_cs;
		break;
	case MSR_IA32_SYSENTER_EIP:
		*data = svm->sysenter_eip;
		break;
	case MSR_IA32_SYSENTER_ESP:
		*data = svm->sysenter_esp;
		break;
	/*
	 * Nobody will change the following 5 values in the VMCB so we can
	 * safely return them on rdmsr. They will always be 0 until LBRV is
	 * implemented.
	 */
	case MSR_IA32_DEBUGCTLMSR:
		*data = svm->vmcb->save.dbgctl;
		break;
	case MSR_IA32_LASTBRANCHFROMIP:
		*data = svm->vmcb->save.br_from;
		break;
	case MSR_IA32_LASTBRANCHTOIP:
		*data = svm->vmcb->save.br_to;
		break;
	case MSR_IA32_LASTINTFROMIP:
		*data = svm->vmcb->save.last_excp_from;
		break;
	case MSR_IA32_LASTINTTOIP:
		*data = svm->vmcb->save.last_excp_to;
		break;
	case MSR_VM_HSAVE_PA:
		*data = svm->nested.hsave_msr;
		break;
	case MSR_VM_CR:
		*data = svm->nested.vm_cr_msr;
		break;
	case MSR_IA32_UCODE_REV:
		*data = 0x01000065;
		break;
	default:
		return kvm_get_msr_common(vcpu, ecx, data);
	}
	return 0;
}

static int svm_get_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 *data)
{
	struct vcpu_svm *svm = to_svm(vcpu);

	switch (ecx) {
	case MSR_IA32_TSC: {
		*data = svm->vmcb->control.tsc_offset +
			svm_scale_tsc(vcpu, native_read_tsc());

		break;
	}
	case MSR_STAR:
		*data = svm->vmcb->save.star;
		break;
#ifdef CONFIG_X86_64
	case MSR_LSTAR:
		*data = svm->vmcb->save.lstar;
		break;
	case MSR_CSTAR:
		*data = svm->vmcb->save.cstar;
		break;
	case MSR_KERNEL_GS_BASE:
		*data = svm->vmcb->save.kernel_gs_base;
		break;
	case MSR_SYSCALL_MASK:
		*data = svm->vmcb->save.sfmask;
		break;
#endif
	case MSR_IA32_SYSENTER_CS:
		*data = svm->vmcb->save.sysenter_cs;
		break;
	case MSR_IA32_SYSENTER_EIP:
		*data = svm->sysenter_eip;
		break;
	case MSR_IA32_SYSENTER_ESP:
		*data = svm->sysenter_esp;
		break;
	/*
	 * Nobody will change the following 5 values in the VMCB so we can
	 * safely return them on rdmsr. They will always be 0 until LBRV is
	 * implemented.
	 */
	case MSR_IA32_DEBUGCTLMSR:
		*data = svm->vmcb->save.dbgctl;
		break;
	case MSR_IA32_LASTBRANCHFROMIP:
		*data = svm->vmcb->save.br_from;
		break;
	case MSR_IA32_LASTBRANCHTOIP:
		*data = svm->vmcb->save.br_to;
		break;
	case MSR_IA32_LASTINTFROMIP:
		*data = svm->vmcb->save.last_excp_from;
		break;
	case MSR_IA32_LASTINTTOIP:
		*data = svm->vmcb->save.last_excp_to;
		break;
	case MSR_VM_HSAVE_PA:
		*data = svm->nested.hsave_msr;
		break;
	case MSR_VM_CR:
		*data = svm->nested.vm_cr_msr;
		break;
	case MSR_IA32_UCODE_REV:
		*data = 0x01000065;
		break;
	default:
		return kvm_get_msr_common(vcpu, ecx, data);
	}
	return 0;
}
