KVM: x86: Fix uninitialized op->type for some immediate values
The emulator could reuse an op->type from a previous instruction for some
immediate values. If it mistakenly considers the operands as memory
operands, it will performs a memory read and overwrite op->val.
Consider for instance the ROR instruction - src2 (the number of times)
would be read from memory instead of being used as immediate.
Mark every immediate operand as such to avoid this problem.
Cc: stable@vger.kernel.org
Fixes: c44b4c6ab80eef3a9c52c7b3f0c632942e6489aa
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 5edf088..9f8a2fa 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4287,6 +4287,7 @@
fetch_register_operand(op);
break;
case OpCL:
+ op->type = OP_IMM;
op->bytes = 1;
op->val = reg_read(ctxt, VCPU_REGS_RCX) & 0xff;
break;
@@ -4294,6 +4295,7 @@
rc = decode_imm(ctxt, op, 1, true);
break;
case OpOne:
+ op->type = OP_IMM;
op->bytes = 1;
op->val = 1;
break;
@@ -4352,21 +4354,27 @@
ctxt->memop.bytes = ctxt->op_bytes + 2;
goto mem_common;
case OpES:
+ op->type = OP_IMM;
op->val = VCPU_SREG_ES;
break;
case OpCS:
+ op->type = OP_IMM;
op->val = VCPU_SREG_CS;
break;
case OpSS:
+ op->type = OP_IMM;
op->val = VCPU_SREG_SS;
break;
case OpDS:
+ op->type = OP_IMM;
op->val = VCPU_SREG_DS;
break;
case OpFS:
+ op->type = OP_IMM;
op->val = VCPU_SREG_FS;
break;
case OpGS:
+ op->type = OP_IMM;
op->val = VCPU_SREG_GS;
break;
case OpImplicit: