From: Nadav Amit <namit@cs.technion.ac.il>
Date: Thu, 2 Oct 2014 22:10:03 +0000 (+0300)
Subject: KVM: x86: Emulator performs code segment checks on read access
X-Git-Tag: v3.19-rc1~36^2~105
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=c49c759f7a68b70d2fed019760a66843b3df39b8;p=linux.git

KVM: x86: Emulator performs code segment checks on read access

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>
---

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index bdd4197e31fa..cd2029bbab48 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -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)) {