linux-kernel - [PATCH 4.19 166/211] KVM: x86: set ctxt->have_exception in x86_decode

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Message-Id: <20191003154525.759012107@linuxfoundation.org>
Date:   Thu,  3 Oct 2019 17:53:52 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Denis Lunev <den@...tuozzo.com>,
        Roman Kagan <rkagan@...tuozzo.com>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>,
        Jan Dakinevich <jan.dakinevich@...tuozzo.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: [PATCH 4.19 166/211] KVM: x86: set ctxt->have_exception in x86_decode_insn()

From: Jan Dakinevich <jan.dakinevich@...tuozzo.com>

commit c8848cee74ff05638e913582a476bde879c968ad upstream.

x86_emulate_instruction() takes into account ctxt->have_exception flag
during instruction decoding, but in practice this flag is never set in
x86_decode_insn().

Fixes: 6ea6e84309ca ("KVM: x86: inject exceptions produced by x86_decode_insn")
Cc: stable@...r.kernel.org
Cc: Denis Lunev <den@...tuozzo.com>
Cc: Roman Kagan <rkagan@...tuozzo.com>
Cc: Denis Plotnikov <dplotnikov@...tuozzo.com>
Signed-off-by: Jan Dakinevich <jan.dakinevich@...tuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/x86/kvm/emulate.c |    2 ++
 arch/x86/kvm/x86.c     |    6 ++++++
 2 files changed, 8 insertions(+)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5368,6 +5368,8 @@ done_prefixes:
 					ctxt->memopp->addr.mem.ea + ctxt->_eip);
 
 done:
+	if (rc == X86EMUL_PROPAGATE_FAULT)
+		ctxt->have_exception = true;
 	return (rc != X86EMUL_CONTINUE) ? EMULATION_FAILED : EMULATION_OK;
 }
 
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6245,6 +6245,12 @@ int x86_emulate_instruction(struct kvm_v
 						emulation_type))
 				return EMULATE_DONE;
 			if (ctxt->have_exception) {
+				/*
+				 * #UD should result in just EMULATION_FAILED, and trap-like
+				 * exception should not be encountered during decode.
+				 */
+				WARN_ON_ONCE(ctxt->exception.vector == UD_VECTOR ||
+					     exception_type(ctxt->exception.vector) == EXCPT_TRAP);
 				inject_emulated_exception(vcpu);
 				return EMULATE_DONE;
 			}