acpi: acpica: fix acpi parse and parseext cache leaks

I'm Seunghun Han, and I work for National Security Research Institute of
South Korea.

I have been doing a research on ACPI and found an ACPI cache leak in ACPI
early abort cases.

Boot log of ACPI cache leak is as follows:
[    0.352414] ACPI: Added _OSI(Module Device)
[    0.353182] ACPI: Added _OSI(Processor Device)
[    0.353182] ACPI: Added _OSI(3.0 _SCP Extensions)
[    0.353182] ACPI: Added _OSI(Processor Aggregator Device)
[    0.356028] ACPI: Unable to start the ACPI Interpreter
[    0.356799] ACPI Error: Could not remove SCI handler (20170303/evmisc-281)
[    0.360215] kmem_cache_destroy Acpi-State: Slab cache still has objects
[    0.360648] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G        W
4.12.0-rc4-next-20170608+ #10
[    0.361273] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
VirtualBox 12/01/2006
[    0.361873] Call Trace:
[    0.362243]  ? dump_stack+0x5c/0x81
[    0.362591]  ? kmem_cache_destroy+0x1aa/0x1c0
[    0.362944]  ? acpi_sleep_proc_init+0x27/0x27
[    0.363296]  ? acpi_os_delete_cache+0xa/0x10
[    0.363646]  ? acpi_ut_delete_caches+0x6d/0x7b
[    0.364000]  ? acpi_terminate+0xa/0x14
[    0.364000]  ? acpi_init+0x2af/0x34f
[    0.364000]  ? __class_create+0x4c/0x80
[    0.364000]  ? video_setup+0x7f/0x7f
[    0.364000]  ? acpi_sleep_proc_init+0x27/0x27
[    0.364000]  ? do_one_initcall+0x4e/0x1a0
[    0.364000]  ? kernel_init_freeable+0x189/0x20a
[    0.364000]  ? rest_init+0xc0/0xc0
[    0.364000]  ? kernel_init+0xa/0x100
[    0.364000]  ? ret_from_fork+0x25/0x30

I analyzed this memory leak in detail. I found that “Acpi-State” cache and
“Acpi-Parse” cache were merged because the size of cache objects was same
slab cache size.

I finally found “Acpi-Parse” cache and “Acpi-ParseExt” cache were leaked
using SLAB_NEVER_MERGE flag in kmem_cache_create() function.

Real ACPI cache leak point is as follows:
[    0.360101] ACPI: Added _OSI(Module Device)
[    0.360101] ACPI: Added _OSI(Processor Device)
[    0.360101] ACPI: Added _OSI(3.0 _SCP Extensions)
[    0.361043] ACPI: Added _OSI(Processor Aggregator Device)
[    0.364016] ACPI: Unable to start the ACPI Interpreter
[    0.365061] ACPI Error: Could not remove SCI handler (20170303/evmisc-281)
[    0.368174] kmem_cache_destroy Acpi-Parse: Slab cache still has objects
[    0.369332] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W
4.12.0-rc4-next-20170608+ #8
[    0.371256] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
VirtualBox 12/01/2006
[    0.372000] Call Trace:
[    0.372000]  ? dump_stack+0x5c/0x81
[    0.372000]  ? kmem_cache_destroy+0x1aa/0x1c0
[    0.372000]  ? acpi_sleep_proc_init+0x27/0x27
[    0.372000]  ? acpi_os_delete_cache+0xa/0x10
[    0.372000]  ? acpi_ut_delete_caches+0x56/0x7b
[    0.372000]  ? acpi_terminate+0xa/0x14
[    0.372000]  ? acpi_init+0x2af/0x34f
[    0.372000]  ? __class_create+0x4c/0x80
[    0.372000]  ? video_setup+0x7f/0x7f
[    0.372000]  ? acpi_sleep_proc_init+0x27/0x27
[    0.372000]  ? do_one_initcall+0x4e/0x1a0
[    0.372000]  ? kernel_init_freeable+0x189/0x20a
[    0.372000]  ? rest_init+0xc0/0xc0
[    0.372000]  ? kernel_init+0xa/0x100
[    0.372000]  ? ret_from_fork+0x25/0x30
[    0.388039] kmem_cache_destroy Acpi-ParseExt: Slab cache still has objects
[    0.389063] CPU: 1 PID: 1 Comm: swapper/0 Tainted: G        W
4.12.0-rc4-next-20170608+ #8
[    0.390557] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS
VirtualBox 12/01/2006
[    0.392000] Call Trace:
[    0.392000]  ? dump_stack+0x5c/0x81
[    0.392000]  ? kmem_cache_destroy+0x1aa/0x1c0
[    0.392000]  ? acpi_sleep_proc_init+0x27/0x27
[    0.392000]  ? acpi_os_delete_cache+0xa/0x10
[    0.392000]  ? acpi_ut_delete_caches+0x6d/0x7b
[    0.392000]  ? acpi_terminate+0xa/0x14
[    0.392000]  ? acpi_init+0x2af/0x34f
[    0.392000]  ? __class_create+0x4c/0x80
[    0.392000]  ? video_setup+0x7f/0x7f
[    0.392000]  ? acpi_sleep_proc_init+0x27/0x27
[    0.392000]  ? do_one_initcall+0x4e/0x1a0
[    0.392000]  ? kernel_init_freeable+0x189/0x20a
[    0.392000]  ? rest_init+0xc0/0xc0
[    0.392000]  ? kernel_init+0xa/0x100
[    0.392000]  ? ret_from_fork+0x25/0x30

When early abort is occurred due to invalid ACPI information, Linux kernel
terminates ACPI by calling acpi_terminate() function. The function calls
acpi_ut_delete_caches() function to delete local caches (acpi_gbl_namespace_
cache, state_cache, operand_cache, ps_node_cache, ps_node_ext_cache).

But the deletion codes in acpi_ut_delete_caches() function only delete
slab caches using kmem_cache_destroy() function, therefore the cache
objects should be flushed before acpi_ut_delete_caches() function.

“Acpi-Parse” cache and “Acpi-ParseExt” cache are used in an AML parse
function, acpi_ps_parse_loop(). The function should have flush codes to
handle an error state due to invalid AML codes.

This cache leak has 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.

To fix ACPI cache leak for enhancing security, I made a patch which has
flush codes in acpi_ps_parse_loop() function.

I hope that this patch improves the security of Linux kernel.

Thank you.

Signed-off-by: Seunghun Han <kkamagui@gmail.com>
AcpiPsGetAmlOpcode (
    ACPI_WALK_STATE         *WalkState)
{
    UINT32                  AmlOffset;


    ACPI_FUNCTION_TRACE_PTR (PsGetAmlOpcode, WalkState);


    WalkState->Aml = WalkState->ParserState.Aml;
    WalkState->Opcode = AcpiPsPeekOpcode (&(WalkState->ParserState));

    /*
     * First cut to determine what we have found:
     * 1) A valid AML opcode
     * 2) A name string
     * 3) An unknown/invalid opcode
     */
    WalkState->OpInfo = AcpiPsGetOpcodeInfo (WalkState->Opcode);

    switch (WalkState->OpInfo->Class)
    {
    case AML_CLASS_ASCII:
    case AML_CLASS_PREFIX:
        /*
         * Starts with a valid prefix or ASCII char, this is a name
         * string. Convert the bare name string to a namepath.
         */
        WalkState->Opcode = AML_INT_NAMEPATH_OP;
        WalkState->ArgTypes = ARGP_NAMESTRING;
        break;

    case AML_CLASS_UNKNOWN:

        /* The opcode is unrecognized. Complain and skip unknown opcodes */

        if (WalkState->PassNumber == 2)
        {
            AmlOffset = (UINT32) ACPI_PTR_DIFF (WalkState->Aml,
                WalkState->ParserState.AmlStart);

            ACPI_ERROR ((AE_INFO,
                "Unknown opcode 0x%.2X at table offset 0x%.4X, ignoring",
                WalkState->Opcode,
                (UINT32) (AmlOffset + sizeof (ACPI_TABLE_HEADER))));

            ACPI_DUMP_BUFFER ((WalkState->ParserState.Aml - 16), 48);

#ifdef ACPI_ASL_COMPILER
            /*
             * This is executed for the disassembler only. Output goes
             * to the disassembled ASL output file.
             */
            AcpiOsPrintf (
                "/*\nError: Unknown opcode 0x%.2X at table offset 0x%.4X, context:\n",
                WalkState->Opcode,
                (UINT32) (AmlOffset + sizeof (ACPI_TABLE_HEADER)));

            ACPI_ERROR ((AE_INFO,
                "Aborting disassembly, AML byte code is corrupt"));

            /* Dump the context surrounding the invalid opcode */

            AcpiUtDumpBuffer (((UINT8 *) WalkState->ParserState.Aml - 16),
                48, DB_BYTE_DISPLAY,
                (AmlOffset + sizeof (ACPI_TABLE_HEADER) - 16));
            AcpiOsPrintf (" */\n");

            /*
             * Just abort the disassembly, cannot continue because the
             * parser is essentially lost. The disassembler can then
             * randomly fail because an ill-constructed parse tree
             * can result.
             */
            return_ACPI_STATUS (AE_AML_BAD_OPCODE);
#endif
        }

        /* Increment past one-byte or two-byte opcode */

        WalkState->ParserState.Aml++;
        if (WalkState->Opcode > 0xFF) /* Can only happen if first byte is 0x5B */
        {
            WalkState->ParserState.Aml++;
        }

        return_ACPI_STATUS (AE_CTRL_PARSE_CONTINUE);

    default:

        /* Found opcode info, this is a normal opcode */

        WalkState->ParserState.Aml +=
            AcpiPsGetOpcodeSize (WalkState->Opcode);
        WalkState->ArgTypes = WalkState->OpInfo->ParseArgs;
        break;
    }

    return_ACPI_STATUS (AE_OK);
}

AcpiPsGetAmlOpcode (
    ACPI_WALK_STATE         *WalkState)
{
    UINT32                  AmlOffset;


    ACPI_FUNCTION_TRACE_PTR (PsGetAmlOpcode, WalkState);


    WalkState->Aml = WalkState->ParserState.Aml;
    WalkState->Opcode = AcpiPsPeekOpcode (&(WalkState->ParserState));

    /*
     * First cut to determine what we have found:
     * 1) A valid AML opcode
     * 2) A name string
     * 3) An unknown/invalid opcode
     */
    WalkState->OpInfo = AcpiPsGetOpcodeInfo (WalkState->Opcode);

    switch (WalkState->OpInfo->Class)
    {
    case AML_CLASS_ASCII:
    case AML_CLASS_PREFIX:
        /*
         * Starts with a valid prefix or ASCII char, this is a name
         * string. Convert the bare name string to a namepath.
         */
        WalkState->Opcode = AML_INT_NAMEPATH_OP;
        WalkState->ArgTypes = ARGP_NAMESTRING;
        break;

    case AML_CLASS_UNKNOWN:

        /* The opcode is unrecognized. Complain and skip unknown opcodes */

        if (WalkState->PassNumber == 2)
        {
            AmlOffset = (UINT32) ACPI_PTR_DIFF (WalkState->Aml,
                WalkState->ParserState.AmlStart);

            ACPI_ERROR ((AE_INFO,
                "Unknown opcode 0x%.2X at table offset 0x%.4X, ignoring",
                WalkState->Opcode,
                (UINT32) (AmlOffset + sizeof (ACPI_TABLE_HEADER))));

            ACPI_DUMP_BUFFER ((WalkState->ParserState.Aml - 16), 48);

#ifdef ACPI_ASL_COMPILER
            /*
             * This is executed for the disassembler only. Output goes
             * to the disassembled ASL output file.
             */
            AcpiOsPrintf (
                "/*\nError: Unknown opcode 0x%.2X at table offset 0x%.4X, context:\n",
                WalkState->Opcode,
                (UINT32) (AmlOffset + sizeof (ACPI_TABLE_HEADER)));

            ACPI_ERROR ((AE_INFO,
                "Aborting disassembly, AML byte code is corrupt"));

            /* Dump the context surrounding the invalid opcode */

            AcpiUtDumpBuffer (((UINT8 *) WalkState->ParserState.Aml - 16),
                48, DB_BYTE_DISPLAY,
                (AmlOffset + sizeof (ACPI_TABLE_HEADER) - 16));
            AcpiOsPrintf (" */\n");

            /*
             * Just abort the disassembly, cannot continue because the
             * parser is essentially lost. The disassembler can then
             * randomly fail because an ill-constructed parse tree
             * can result.
             */
            return_ACPI_STATUS (AE_AML_BAD_OPCODE);
#endif
        }

        /* Increment past one-byte or two-byte opcode */

        WalkState->ParserState.Aml++;
        if (WalkState->Opcode > 0xFF) /* Can only happen if first byte is 0x5B */
        {
            WalkState->ParserState.Aml++;
        }

        return_ACPI_STATUS (AE_CTRL_PARSE_CONTINUE);

    default:

        /* Found opcode info, this is a normal opcode */

        WalkState->ParserState.Aml +=
            AcpiPsGetOpcodeSize (WalkState->Opcode);
        WalkState->ArgTypes = WalkState->OpInfo->ParseArgs;
        break;
    }

    return_ACPI_STATUS (AE_OK);
}
