[PATCH 3.17 041/141] KVM: x86: Fix uninitialized op->type for some immediate values

Greg Kroah-Hartman
2014-11-19T22:24:30Z

From: Nadav Amit <namit@cs.technion.ac.il>

commit d29b9d7ed76c0b961603ca692b8a562556a20212 upstream.

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.

Fixes: c44b4c6ab80eef3a9c52c7b3f0c632942e6489aa
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 | 8 ++++++++
1 file changed, 8 insertions(+)

--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -4272,6 +4272,7 @@ static int decode_operand(struct x86_emu
fetch_register_operand(op);
break;
case OpCL:
+ op->type = OP_IMM;
op->bytes = 1;
op->val = reg_read(ctxt, VCPU_REGS_RCX) & 0xff;
break;
@@ -4279,6 +4280,7 @@ static int decode_operand(struct x86_emu
rc = decode_imm(ctxt, op, 1, true);
break;
case OpOne:
+ op->type = OP_IMM;
op->bytes = 1;
op->val = 1;
break;
@@ -4337,21 +4339,27 @@ static int decode_operand(struct x86_emu
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;