| From | Greg Kroah-Hartman <> | Subject | [PATCH 3.16 056/125] KVM: x86: Inter-privilege level ret emulation is not implemeneted | Date | Wed, 3 Sep 2014 15:06:53 -0700 |
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3.16-stable review patch. If anyone has any objections, please let me know.
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From: Nadav Amit <namit@cs.technion.ac.il>
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@cs.technion.ac.il> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/x86/kvm/emulate.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2017,6 +2017,7 @@ 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) @@ -2026,6 +2027,9 @@ 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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