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    Subject[PATCH 3.4 152/177] KVM: x86: Fix uninitialized op->type for some immediate values
    Date
    From: Nadav Amit <namit@cs.technion.ac.il>

    3.4.106-rc1 review patch. If anyone has any objections, please let me know.

    ------------------


    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: Zefan Li <lizefan@huawei.com>
    ---
    arch/x86/kvm/emulate.c | 8 ++++++++
    1 file changed, 8 insertions(+)

    diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
    index e125c3e..0a12507 100644
    --- a/arch/x86/kvm/emulate.c
    +++ b/arch/x86/kvm/emulate.c
    @@ -3833,6 +3833,7 @@ 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 = ctxt->regs[VCPU_REGS_RCX] & 0xff;
    break;
    @@ -3840,6 +3841,7 @@ 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;
    @@ -3879,21 +3881,27 @@ 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:
    --
    1.9.1


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