From 3a6095a0173ad8f20c508446880558c9f9224324 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Wed, 13 Aug 2014 16:50:13 +0300 Subject: [PATCH] KVM: x86: Avoid emulating instructions on #UD mistakenly Commit d40a6898e5 mistakenly caused instructions which are not marked as EmulateOnUD to be emulated upon #UD exception. The commit caused the check of whether the instruction flags include EmulateOnUD to never be evaluated. As a result instructions whose emulation is broken may be emulated. This fix moves the evaluation of EmulateOnUD so it would be evaluated. Signed-off-by: Nadav Amit [Tweak operand order in &&, remove EmulateOnUD where it's now superfluous. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/emulate.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 56657b0bb3bb..ef117b842334 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4394,8 +4394,11 @@ done_prefixes: ctxt->execute = opcode.u.execute; + if (unlikely(ctxt->ud) && likely(!(ctxt->d & EmulateOnUD))) + return EMULATION_FAILED; + if (unlikely(ctxt->d & - (NotImpl|EmulateOnUD|Stack|Op3264|Sse|Mmx|Intercept|CheckPerm))) { + (NotImpl|Stack|Op3264|Sse|Mmx|Intercept|CheckPerm))) { /* * These are copied unconditionally here, and checked unconditionally * in x86_emulate_insn. @@ -4406,9 +4409,6 @@ done_prefixes: if (ctxt->d & NotImpl) return EMULATION_FAILED; - if (!(ctxt->d & EmulateOnUD) && ctxt->ud) - return EMULATION_FAILED; - if (mode == X86EMUL_MODE_PROT64 && (ctxt->d & Stack)) ctxt->op_bytes = 8;