3.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
commit 9e8919ae793f4edfaa29694a70f71a515ae9942a upstream.
Return unhandlable error on inter-privilege level ret instruction. This is
since the current emulation does not check the privilege level correctly when
loading the CS, and does not pop RSP/SS as needed.
Signed-off-by: Nadav Amit <namit@xxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -2006,6 +2006,7 @@ static int em_ret_far(struct x86_emulate
{
int rc;
unsigned long cs;
+ int cpl = ctxt->ops->cpl(ctxt);
rc = emulate_pop(ctxt, &ctxt->_eip, ctxt->op_bytes);
if (rc != X86EMUL_CONTINUE)
@@ -2015,6 +2016,9 @@ static int em_ret_far(struct x86_emulate
rc = emulate_pop(ctxt, &cs, ctxt->op_bytes);
if (rc != X86EMUL_CONTINUE)
return rc;
+ /* Outer-privilege level return is not implemented */
+ if (ctxt->mode >= X86EMUL_MODE_PROT16 && (cs & 3) > cpl)
+ return X86EMUL_UNHANDLEABLE;
rc = load_segment_descriptor(ctxt, (u16)cs, VCPU_SREG_CS);
return rc;
}
--
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