The address size of an instruction affects the effective address, not
the virtual/linear address. The final address may still be truncated,
e.g. to 32-bits outside of long mode, but that happens irrespective of
the address size, e.g. a 32-bit address size can yield a 64-bit virtual
address when using FS/GS with a non-zero base.
Fixes: 064aea774768 ("KVM: nVMX: Decoding memory operands of VMX instructions")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
---
arch/x86/kvm/vmx/nested.c | 25 +++++++++++++++++++++++--
1 file changed, 23 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 40b6e331dce9..bc8e3fc6724d 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -4039,20 +4039,41 @@ int get_vmx_mem_address(struct kvm_vcpu *vcpu, unsigned long exit_qualification,
if (index_is_valid)
off += kvm_register_read(vcpu, index_reg)<<scaling;
vmx_get_segment(vcpu, &s, seg_reg);
- *ret = s.base + off;
+ /*
+ * The effective address, i.e. @off, of a memory operand is truncated
+ * based on the address size of the instruction. Note that this is
+ * the *effective address*, i.e. the address prior to accounting for
+ * the segment's base.
+ */
if (addr_size == 1) /* 32 bit */
- *ret &= 0xffffffff;
+ off &= 0xffffffff;
+ else if (addr_size == 0) /* 16 bit */
+ off &= 0xffff;
/* Checks for #GP/#SS exceptions. */
exn = false;
if (is_long_mode(vcpu)) {
+ /*
+ * The virtual/linear address is never truncated in 64-bit
+ * mode, e.g. a 32-bit address size can yield a 64-bit virtual
+ * address when using FS/GS with a non-zero base.
+ */
+ *ret = s.base + off;
+
/* Long mode: #GP(0)/#SS(0) if the memory address is in a
* non-canonical form. This is the only check on the memory
* destination for long mode!
*/
exn = is_noncanonical_address(*ret, vcpu);
} else if (is_protmode(vcpu)) {
+ /*
+ * When not in long mode, the virtual/linear address is
+ * unconditionally truncated to 32 bits regardless of the
+ * address size.
+ */
+ *ret = (s.base + off) & 0xffffffff;
+
/* Protected mode: apply checks for segment validity in the
* following order:
* - segment type check (#GP(0) may be thrown)
--
2.20.1
