Commit message: acpi: acpica: fix acpi operand cache leak in nseval.c

I found an ACPI cache leak in ACPI early termination and boot continuing case.

When early termination occurs due to malicious ACPI table, Linux kernel
terminates ACPI function and continues to boot process. While kernel terminates
ACPI function, kmem_cache_destroy() reports Acpi-Operand cache leak.

Boot log of ACPI operand cache leak is as follows:
>[    0.464168] ACPI: Added _OSI(Module Device)
>[    0.467022] ACPI: Added _OSI(Processor Device)
>[    0.469376] ACPI: Added _OSI(3.0 _SCP Extensions)
>[    0.471647] ACPI: Added _OSI(Processor Aggregator Device)
>[    0.477997] ACPI Error: Null stack entry at ffff880215c0aad8 (20170303/exresop-174)
>[    0.482706] ACPI Exception: AE_AML_INTERNAL, While resolving operands for [OpcodeName unavailable] (20170303/dswexec-461)
>[    0.487503] ACPI Error: Method parse/execution failed [\DBG] (Node ffff88021710ab40), AE_AML_INTERNAL (20170303/psparse-543)
>[    0.492136] ACPI Error: Method parse/execution failed [\_SB._INI] (Node ffff88021710a618), AE_AML_INTERNAL (20170303/psparse-543)
>[    0.497683] ACPI: Interpreter enabled
>[    0.499385] ACPI: (supports S0)
>[    0.501151] ACPI: Using IOAPIC for interrupt routing
>[    0.503342] ACPI Error: Null stack entry at ffff880215c0aad8 (20170303/exresop-174)
>[    0.506522] ACPI Exception: AE_AML_INTERNAL, While resolving operands for [OpcodeName unavailable] (20170303/dswexec-461)
>[    0.510463] ACPI Error: Method parse/execution failed [\DBG] (Node ffff88021710ab40), AE_AML_INTERNAL (20170303/psparse-543)
>[    0.514477] ACPI Error: Method parse/execution failed [\_PIC] (Node ffff88021710ab18), AE_AML_INTERNAL (20170303/psparse-543)
>[    0.518867] ACPI Exception: AE_AML_INTERNAL, Evaluating _PIC (20170303/bus-991)
>[    0.522384] kmem_cache_destroy Acpi-Operand: Slab cache still has objects
>[    0.524597] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 4.12.0-rc5 #26
>[    0.526795] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006
>[    0.529668] Call Trace:
>[    0.530811]  ? dump_stack+0x5c/0x81
>[    0.532240]  ? kmem_cache_destroy+0x1aa/0x1c0
>[    0.533905]  ? acpi_os_delete_cache+0xa/0x10
>[    0.535497]  ? acpi_ut_delete_caches+0x3f/0x7b
>[    0.537237]  ? acpi_terminate+0xa/0x14
>[    0.538701]  ? acpi_init+0x2af/0x34f
>[    0.540008]  ? acpi_sleep_proc_init+0x27/0x27
>[    0.541593]  ? do_one_initcall+0x4e/0x1a0
>[    0.543008]  ? kernel_init_freeable+0x19e/0x21f
>[    0.546202]  ? rest_init+0x80/0x80
>[    0.547513]  ? kernel_init+0xa/0x100
>[    0.548817]  ? ret_from_fork+0x25/0x30
>[    0.550587] vgaarb: loaded
>[    0.551716] EDAC MC: Ver: 3.0.0
>[    0.553744] PCI: Probing PCI hardware
>[    0.555038] PCI host bridge to bus 0000:00
> ... Continue to boot and log is omitted ...

I analyzed this memory leak in detail and found AcpiNsEvaluate() function
only removes Info->ReturnObject in AE_CTRL_RETURN_VALUE case. But, when errors
occur, the status value is not AE_CTRL_RETURN_VALUE, and Info->ReturnObject is
also not null. Therefore, this causes acpi operand memory leak.

This cache leak causes a security threat because an old kernel (<= 4.9) shows
memory locations of kernel functions in stack dump. Some malicious users
could use this information to neutralize kernel ASLR.

I made a patch to fix ACPI operand cache leak.

Signed-off-by: Seunghun Han <kkamagui@gmail.com>
CVE: CVE-2017-13695
CWE: CWE-200
Vulnerability description: The acpi_ns_evaluate() function in drivers/acpi/acpica/nseval.c in the Linux kernel through 4.12.9 does not flush the operand cache and causes a kernel stack dump, which allows local users to obtain sensitive information from kernel memory and bypass the KASLR protection mechanism (in the kernel through 4.9) via a crafted ACPI table.

Project: acpica
File: nseval.c

AcpiNsExecModuleCode (
    ACPI_OPERAND_OBJECT     *MethodObj,
    ACPI_EVALUATE_INFO      *Info)
{
    ACPI_OPERAND_OBJECT     *ParentObj;
    ACPI_NAMESPACE_NODE     *ParentNode;
    ACPI_OBJECT_TYPE        Type;
    ACPI_STATUS             Status;


    ACPI_FUNCTION_TRACE (NsExecModuleCode);


    /*
     * Get the parent node. We cheat by using the NextObject field
     * of the method object descriptor.
     */
    ParentNode = ACPI_CAST_PTR (
        ACPI_NAMESPACE_NODE, MethodObj->Method.NextObject);
    Type = AcpiNsGetType (ParentNode);

    /*
     * Get the region handler and save it in the method object. We may need
     * this if an operation region declaration causes a _REG method to be run.
     *
     * We can't do this in AcpiPsLinkModuleCode because
     * AcpiGbl_RootNode->Object is NULL at PASS1.
     */
    if ((Type == ACPI_TYPE_DEVICE) && ParentNode->Object)
    {
        MethodObj->Method.Dispatch.Handler =
            ParentNode->Object->Device.Handler;
    }

    /* Must clear NextObject (AcpiNsAttachObject needs the field) */

    MethodObj->Method.NextObject = NULL;

    /* Initialize the evaluation information block */

    memset (Info, 0, sizeof (ACPI_EVALUATE_INFO));
    Info->PrefixNode = ParentNode;

    /*
     * Get the currently attached parent object. Add a reference,
     * because the ref count will be decreased when the method object
     * is installed to the parent node.
     */
    ParentObj = AcpiNsGetAttachedObject (ParentNode);
    if (ParentObj)
    {
        AcpiUtAddReference (ParentObj);
    }

    /* Install the method (module-level code) in the parent node */

    Status = AcpiNsAttachObject (ParentNode, MethodObj, ACPI_TYPE_METHOD);
    if (ACPI_FAILURE (Status))
    {
        goto Exit;
    }

    /* Execute the parent node as a control method */

    Status = AcpiNsEvaluate (Info);

    ACPI_DEBUG_PRINT ((ACPI_DB_INIT_NAMES,
        "Executed module-level code at %p\n",
        MethodObj->Method.AmlStart));

    /* Delete a possible implicit return value (in slack mode) */

    if (Info->ReturnObject)
    {
        AcpiUtRemoveReference (Info->ReturnObject);
    }

    /* Detach the temporary method object */

    AcpiNsDetachObject (ParentNode);

    /* Restore the original parent object */

    if (ParentObj)
    {
        Status = AcpiNsAttachObject (ParentNode, ParentObj, Type);
    }
    else
    {
        ParentNode->Type = (UINT8) Type;
    }

Exit:
    if (ParentObj)
    {
        AcpiUtRemoveReference (ParentObj);
    }
    return_VOID;
}

Project: acpica
File: nseval.c

AcpiNsExecModuleCodeList (
    void)
{
    ACPI_OPERAND_OBJECT     *Prev;
    ACPI_OPERAND_OBJECT     *Next;
    ACPI_EVALUATE_INFO      *Info;
    UINT32                  MethodCount = 0;


    ACPI_FUNCTION_TRACE (NsExecModuleCodeList);


    /* Exit now if the list is empty */

    Next = AcpiGbl_ModuleCodeList;
    if (!Next)
    {
        return_VOID;
    }

    /* Allocate the evaluation information block */

    Info = ACPI_ALLOCATE (sizeof (ACPI_EVALUATE_INFO));
    if (!Info)
    {
        return_VOID;
    }

    /* Walk the list, executing each "method" */

    while (Next)
    {
        Prev = Next;
        Next = Next->Method.Mutex;

        /* Clear the link field and execute the method */

        Prev->Method.Mutex = NULL;
        AcpiNsExecModuleCode (Prev, Info);
        MethodCount++;

        /* Delete the (temporary) method object */

        AcpiUtRemoveReference (Prev);
    }

    ACPI_INFO ((
        "Executed %u blocks of module-level executable AML code",
        MethodCount));

    ACPI_FREE (Info);
    AcpiGbl_ModuleCodeList = NULL;
    return_VOID;
}