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KVM: x86: Fix uninitialized op->type for some immediate values

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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: c44b4c6ab8
Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nadav Amit 2014-11-02 11:54:47 +02:00 committed by Paolo Bonzini
parent bc79a3179a
commit d29b9d7ed7
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kvm/emulate.c
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@ -4287,6 +4287,7 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
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 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
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 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
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: