KVM: x86: Emulator performs code segment checks on read access
authorNadav Amit <namit@cs.technion.ac.il>
Thu, 2 Oct 2014 22:10:03 +0000 (01:10 +0300)
committerPaolo Bonzini <pbonzini@redhat.com>
Mon, 3 Nov 2014 11:07:25 +0000 (12:07 +0100)
When read access is performed using a readable code segment, the "conforming"
and "non-conforming" checks should not be done.  As a result, read using
non-conforming readable code segment fails.

This is according to Intel SDM 5.6.1 ("Accessing Data in Code Segments").

The fix is not to perform the "non-conforming" checks if the access is not a
fetch; the relevant checks are already done when loading the segment.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
arch/x86/kvm/emulate.c

index bdd4197..cd2029b 100644 (file)
@@ -703,8 +703,8 @@ static __always_inline int __linearize(struct x86_emulate_ctxt *ctxt,
                if (size > *max_size)
                        goto bad;
                cpl = ctxt->ops->cpl(ctxt);
-               if (!(desc.type & 8)) {
-                       /* data segment */
+               if (!fetch) {
+                       /* data segment or readable code segment */
                        if (cpl > desc.dpl)
                                goto bad;
                } else if ((desc.type & 8) && !(desc.type & 4)) {