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Commit f9eb4af6 authored by Eugene Korenevsky's avatar Eugene Korenevsky Committed by Paolo Bonzini
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KVM: nVMX: VMX instructions: add checks for #GP/#SS exceptions 



According to Intel SDM several checks must be applied for memory operands
of VMX instructions.

Long mode: #GP(0) or #SS(0) depending on the segment must be thrown
if the memory address is in a non-canonical form.

Protected mode, checks in chronological order:
- The segment type must be checked with access type (read or write) taken
into account.
	For write access: #GP(0) must be generated if the destination operand
		is located in a read-only data segment or any code segment.
	For read access: #GP(0) must be generated if if the source operand is
		located in an execute-only code segment.
- Usability of the segment must be checked. #GP(0) or #SS(0) depending on the
	segment must be thrown if the segment is unusable.
- Limit check. #GP(0) or #SS(0) depending on the segment must be
	thrown if the memory operand effective address is outside the segment
	limit.

Signed-off-by: default avatarEugene Korenevsky <ekorenevsky@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 0da029ed

arch/x86/kvm/vmx.c

+61 −16
Original line number Diff line number Diff line
@@ -6408,8 +6408,12 @@ static enum hrtimer_restart vmx_preemption_timer_fn(struct hrtimer *timer) 
 */

static int get_vmx_mem_address(struct kvm_vcpu *vcpu,

				 unsigned long exit_qualification,

				 u32 vmx_instruction_info, gva_t *ret)

				 u32 vmx_instruction_info, bool wr, gva_t *ret)

{

	gva_t off;

	bool exn;

	struct kvm_segment s;



	/*

	 * According to Vol. 3B, "Information for VM Exits Due to Instruction

	 * Execution", on an exit, vmx_instruction_info holds most of the
@@ -6434,22 +6438,63 @@ static int get_vmx_mem_address(struct kvm_vcpu *vcpu, 


	/* Addr = segment_base + offset */

	/* offset = base + [index * scale] + displacement */

	*ret = vmx_get_segment_base(vcpu, seg_reg);

	off = exit_qualification; /* holds the displacement */

	if (base_is_valid)

		*ret += kvm_register_read(vcpu, base_reg);

		off += kvm_register_read(vcpu, base_reg);

	if (index_is_valid)

		*ret += kvm_register_read(vcpu, index_reg)<<scaling;

	*ret += exit_qualification; /* holds the displacement */

		off += kvm_register_read(vcpu, index_reg)<<scaling;

	vmx_get_segment(vcpu, &s, seg_reg);

	*ret = s.base + off;



	if (addr_size == 1) /* 32 bit */

		*ret &= 0xffffffff;



	/*

	 * TODO: throw #GP (and return 1) in various cases that the VM*

	 * instructions require it - e.g., offset beyond segment limit,

	 * unusable or unreadable/unwritable segment, non-canonical 64-bit

	 * address, and so on. Currently these are not checked.

	/* Checks for #GP/#SS exceptions. */

	exn = false;

	if (is_protmode(vcpu)) {

		/* Protected mode: apply checks for segment validity in the

		 * following order:

		 * - segment type check (#GP(0) may be thrown)

		 * - usability check (#GP(0)/#SS(0))

		 * - limit check (#GP(0)/#SS(0))

		 */

		if (wr)

			/* #GP(0) if the destination operand is located in a

			 * read-only data segment or any code segment.

			 */

			exn = ((s.type & 0xa) == 0 || (s.type & 8));

		else

			/* #GP(0) if the source operand is located in an

			 * execute-only code segment

			 */

			exn = ((s.type & 0xa) == 8);

	}

	if (exn) {

		kvm_queue_exception_e(vcpu, GP_VECTOR, 0);

		return 1;

	}

	if (is_long_mode(vcpu)) {

		/* Long mode: #GP(0)/#SS(0) if the memory address is in a

		 * non-canonical form. This is an only check for long mode.

		 */

		exn = is_noncanonical_address(*ret);

	} else if (is_protmode(vcpu)) {

		/* Protected mode: #GP(0)/#SS(0) if the segment is unusable.

		 */

		exn = (s.unusable != 0);

		/* Protected mode: #GP(0)/#SS(0) if the memory

		 * operand is outside the segment limit.

		 */

		exn = exn || (off + sizeof(u64) > s.limit);

	}

	if (exn) {

		kvm_queue_exception_e(vcpu,

				      seg_reg == VCPU_SREG_SS ?

						SS_VECTOR : GP_VECTOR,

				      0);

		return 1;

	}



	return 0;

}
@@ -6471,7 +6516,7 @@ static int nested_vmx_check_vmptr(struct kvm_vcpu *vcpu, int exit_reason, 
	int maxphyaddr = cpuid_maxphyaddr(vcpu);



	if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),

			vmcs_read32(VMX_INSTRUCTION_INFO), &gva))

			vmcs_read32(VMX_INSTRUCTION_INFO), false, &gva))

		return 1;



	if (kvm_read_guest_virt(&vcpu->arch.emulate_ctxt, gva, &vmptr,
@@ -6999,7 +7044,7 @@ static int handle_vmread(struct kvm_vcpu *vcpu) 
			field_value);

	} else {

		if (get_vmx_mem_address(vcpu, exit_qualification,

				vmx_instruction_info, &gva))

				vmx_instruction_info, true, &gva))

			return 1;

		/* _system ok, as nested_vmx_check_permission verified cpl=0 */

		kvm_write_guest_virt_system(&vcpu->arch.emulate_ctxt, gva,
@@ -7036,7 +7081,7 @@ static int handle_vmwrite(struct kvm_vcpu *vcpu) 
			(((vmx_instruction_info) >> 3) & 0xf));

	else {

		if (get_vmx_mem_address(vcpu, exit_qualification,

				vmx_instruction_info, &gva))

				vmx_instruction_info, false, &gva))

			return 1;

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

			   &field_value, (is_64_bit_mode(vcpu) ? 8 : 4), &e)) {
@@ -7128,7 +7173,7 @@ static int handle_vmptrst(struct kvm_vcpu *vcpu) 
		return 1;



	if (get_vmx_mem_address(vcpu, exit_qualification,

			vmx_instruction_info, &vmcs_gva))

			vmx_instruction_info, true, &vmcs_gva))

		return 1;

	/* ok to use *_system, as nested_vmx_check_permission verified cpl=0 */

	if (kvm_write_guest_virt_system(&vcpu->arch.emulate_ctxt, vmcs_gva,
@@ -7184,7 +7229,7 @@ static int handle_invept(struct kvm_vcpu *vcpu) 
	 * operand is read even if it isn't needed (e.g., for type==global)

	 */

	if (get_vmx_mem_address(vcpu, vmcs_readl(EXIT_QUALIFICATION),

			vmx_instruction_info, &gva))

			vmx_instruction_info, false, &gva))

		return 1;

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

				sizeof(operand), &e)) {