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: Eugene Korenevsky <ekorenevsky@xxxxxxxxx>
---
arch/x86/kvm/vmx.c | 77 ++++++++++++++++++++++++++++++++++++++++++------------
1 file changed, 61 insertions(+), 16 deletions(-)
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 8c14d6a..08a721e 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6404,8 +6404,12 @@ 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
@@ -6430,22 +6434,63 @@ 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;
}
@@ -6467,7 +6512,7 @@ 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,
@@ -6995,7 +7040,7 @@ 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,
@@ -7032,7 +7077,7 @@ 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)) {
@@ -7124,7 +7169,7 @@ 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,
@@ -7180,7 +7225,7 @@ 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)) {
--
2.0.5
--
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