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Commit cbf71279 authored by Radim Krčmář's avatar Radim Krčmář Committed by Paolo Bonzini
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KVM: nVMX: fix nested_vmx_check_vmptr failure paths under debugging 



kvm_skip_emulated_instruction() will return 0 if userspace is
single-stepping the guest.

kvm_skip_emulated_instruction() uses return status convention of exit
handler: 0 means "exit to userspace" and 1 means "continue vm entries".
The problem is that nested_vmx_check_vmptr() return status means
something else: 0 is ok, 1 is error.

This means we would continue executing after a failure.  Static checker
noticed it because vmptr was not initialized.

Reported-by: default avatarDan Carpenter <dan.carpenter@oracle.com>
Fixes: 6affcbed ("KVM: x86: Add kvm_skip_emulated_instruction and use it.")
Signed-off-by: default avatarRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 52b54190

arch/x86/kvm/vmx.c

+57 −83
Original line number Diff line number Diff line
@@ -6914,97 +6914,21 @@ static int get_vmx_mem_address(struct kvm_vcpu *vcpu, 
	return 0;

}



/*

 * This function performs the various checks including

 * - if it's 4KB aligned

 * - No bits beyond the physical address width are set

 * - Returns 0 on success or else 1

 * (Intel SDM Section 30.3)

 */

static int nested_vmx_check_vmptr(struct kvm_vcpu *vcpu, int exit_reason,

				  gpa_t *vmpointer)

static int nested_vmx_get_vmptr(struct kvm_vcpu *vcpu, gpa_t *vmpointer)

{

	gva_t gva;

	gpa_t vmptr;

	struct x86_exception e;

	struct page *page;

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	int maxphyaddr = cpuid_maxphyaddr(vcpu);



	if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),

			vmcs_read32(VMX_INSTRUCTION_INFO), false, &gva))

		return 1;



	if (kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, gva, &vmptr,

				sizeof(vmptr), &e)) {

	if (kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, gva, vmpointer,

				sizeof(*vmpointer), &e)) {

		kvm_inject_page_fault(vcpu, &e);

		return 1;

	}



	switch (exit_reason) {

	case EXIT_REASON_VMON:

		/*

		 * SDM 3: 24.11.5

		 * The first 4 bytes of VMXON region contain the supported

		 * VMCS revision identifier

		 *

		 * Note - IA32_VMX_BASIC[48] will never be 1

		 * for the nested case;

		 * which replaces physical address width with 32

		 *

		 */

		if (!PAGE_ALIGNED(vmptr) || (vmptr >> maxphyaddr)) {

			nested_vmx_failInvalid(vcpu);

			return kvm_skip_emulated_instruction(vcpu);

		}



		page = nested_get_page(vcpu, vmptr);

		if (page == NULL) {

			nested_vmx_failInvalid(vcpu);

			return kvm_skip_emulated_instruction(vcpu);

		}

		if (*(u32 *)kmap(page) != VMCS12_REVISION) {

			kunmap(page);

			nested_release_page_clean(page);

			nested_vmx_failInvalid(vcpu);

			return kvm_skip_emulated_instruction(vcpu);

		}

		kunmap(page);

		nested_release_page_clean(page);

		vmx->nested.vmxon_ptr = vmptr;

		break;

	case EXIT_REASON_VMCLEAR:

		if (!PAGE_ALIGNED(vmptr) || (vmptr >> maxphyaddr)) {

			nested_vmx_failValid(vcpu,

					     VMXERR_VMCLEAR_INVALID_ADDRESS);

			return kvm_skip_emulated_instruction(vcpu);

		}



		if (vmptr == vmx->nested.vmxon_ptr) {

			nested_vmx_failValid(vcpu,

					     VMXERR_VMCLEAR_VMXON_POINTER);

			return kvm_skip_emulated_instruction(vcpu);

		}

		break;

	case EXIT_REASON_VMPTRLD:

		if (!PAGE_ALIGNED(vmptr) || (vmptr >> maxphyaddr)) {

			nested_vmx_failValid(vcpu,

					     VMXERR_VMPTRLD_INVALID_ADDRESS);

			return kvm_skip_emulated_instruction(vcpu);

		}



		if (vmptr == vmx->nested.vmxon_ptr) {

			nested_vmx_failValid(vcpu,

					     VMXERR_VMPTRLD_VMXON_POINTER);

			return kvm_skip_emulated_instruction(vcpu);

		}

		break;

	default:

		return 1; /* shouldn't happen */

	}



	if (vmpointer)

		*vmpointer = vmptr;

	return 0;

}
@@ -7066,6 +6990,8 @@ static int enter_vmx_operation(struct kvm_vcpu *vcpu) 
static int handle_vmon(struct kvm_vcpu *vcpu)

{

	int ret;

	gpa_t vmptr;

	struct page *page;

	struct vcpu_vmx *vmx = to_vmx(vcpu);

	const u64 VMXON_NEEDED_FEATURES = FEATURE_CONTROL_LOCKED

		| FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
@@ -7095,9 +7021,37 @@ static int handle_vmon(struct kvm_vcpu *vcpu) 
		return 1;

	}



	if (nested_vmx_check_vmptr(vcpu, EXIT_REASON_VMON, NULL))

	if (nested_vmx_get_vmptr(vcpu, &vmptr))

		return 1;



	/*

	 * SDM 3: 24.11.5

	 * The first 4 bytes of VMXON region contain the supported

	 * VMCS revision identifier

	 *

	 * Note - IA32_VMX_BASIC[48] will never be 1 for the nested case;

	 * which replaces physical address width with 32

	 */

	if (!PAGE_ALIGNED(vmptr) || (vmptr >> cpuid_maxphyaddr(vcpu))) {

		nested_vmx_failInvalid(vcpu);

		return kvm_skip_emulated_instruction(vcpu);

	}



	page = nested_get_page(vcpu, vmptr);

	if (page == NULL) {

		nested_vmx_failInvalid(vcpu);

		return kvm_skip_emulated_instruction(vcpu);

	}

	if (*(u32 *)kmap(page) != VMCS12_REVISION) {

		kunmap(page);

		nested_release_page_clean(page);

		nested_vmx_failInvalid(vcpu);

		return kvm_skip_emulated_instruction(vcpu);

	}

	kunmap(page);

	nested_release_page_clean(page);



	vmx->nested.vmxon_ptr = vmptr;

	ret = enter_vmx_operation(vcpu);

	if (ret)

		return ret;
@@ -7213,9 +7167,19 @@ static int handle_vmclear(struct kvm_vcpu *vcpu) 
	if (!nested_vmx_check_permission(vcpu))

		return 1;



	if (nested_vmx_check_vmptr(vcpu, EXIT_REASON_VMCLEAR, &vmptr))

	if (nested_vmx_get_vmptr(vcpu, &vmptr))

		return 1;



	if (!PAGE_ALIGNED(vmptr) || (vmptr >> cpuid_maxphyaddr(vcpu))) {

		nested_vmx_failValid(vcpu, VMXERR_VMCLEAR_INVALID_ADDRESS);

		return kvm_skip_emulated_instruction(vcpu);

	}



	if (vmptr == vmx->nested.vmxon_ptr) {

		nested_vmx_failValid(vcpu, VMXERR_VMCLEAR_VMXON_POINTER);

		return kvm_skip_emulated_instruction(vcpu);

	}



	if (vmptr == vmx->nested.current_vmptr)

		nested_release_vmcs12(vmx);
@@ -7545,9 +7509,19 @@ static int handle_vmptrld(struct kvm_vcpu *vcpu) 
	if (!nested_vmx_check_permission(vcpu))

		return 1;



	if (nested_vmx_check_vmptr(vcpu, EXIT_REASON_VMPTRLD, &vmptr))

	if (nested_vmx_get_vmptr(vcpu, &vmptr))

		return 1;



	if (!PAGE_ALIGNED(vmptr) || (vmptr >> cpuid_maxphyaddr(vcpu))) {

		nested_vmx_failValid(vcpu, VMXERR_VMPTRLD_INVALID_ADDRESS);

		return kvm_skip_emulated_instruction(vcpu);

	}



	if (vmptr == vmx->nested.vmxon_ptr) {

		nested_vmx_failValid(vcpu, VMXERR_VMPTRLD_VMXON_POINTER);

		return kvm_skip_emulated_instruction(vcpu);

	}



	if (vmx->nested.current_vmptr != vmptr) {

		struct vmcs12 *new_vmcs12;

		struct page *page;