KVM: x86: pop sreg accesses only 2 bytes

Although pop sreg updates RSP according to the operand size, only 2 bytes are
read.  The current behavior may result in incorrect #GP or #PF exceptions.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index feaba468cce6..abe95d2e6848 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1828,12 +1828,14 @@ static int em_pop_sreg(struct x86_emulate_ctxt *ctxt)
         unsigned long selector;
         int rc;
 
-        rc = emulate_pop(ctxt, &selector, ctxt->op_bytes);
+        rc = emulate_pop(ctxt, &selector, 2);
         if (rc != X86EMUL_CONTINUE)
                 return rc;
 
         if (ctxt->modrm_reg == VCPU_SREG_SS)
                 ctxt->interruptibility = KVM_X86_SHADOW_INT_MOV_SS;
+        if (ctxt->op_bytes > 2)
+                rsp_increment(ctxt, ctxt->op_bytes - 2);
 
         rc = load_segment_descriptor(ctxt, (u16)selector, seg);
         return rc;