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    Subject[167/197] ACPI: EC: Limit burst to 64 bits
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

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

    From: Alexey Starikovskiy <astarikovskiy@suse.de>

    commit 2060c44576c79086ff24718878d7edaa7384a985 upstream.

    access_bit_width field is u8 in ACPICA, thus 256 value written to it
    becomes 0, causing divide by zero later.

    Proper fix would be to remove access_bit_width at all, just because
    we already have access_byte_width, which is access_bit_width / 8.
    Limit access width to 64 bit for now.

    https://bugzilla.kernel.org/show_bug.cgi?id=15749
    fixes regression caused by the fix for:
    https://bugzilla.kernel.org/show_bug.cgi?id=14667

    Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
    Signed-off-by: Len Brown <len.brown@intel.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/acpi/acpica/exprep.c | 17 +++++++++++------
    1 file changed, 11 insertions(+), 6 deletions(-)

    --- a/drivers/acpi/acpica/exprep.c
    +++ b/drivers/acpi/acpica/exprep.c
    @@ -471,13 +471,18 @@ acpi_status acpi_ex_prep_field_value(str
    /* allow full data read from EC address space */
    if (obj_desc->field.region_obj->region.space_id ==
    ACPI_ADR_SPACE_EC) {
    - if (obj_desc->common_field.bit_length > 8)
    - obj_desc->common_field.access_bit_width =
    - ACPI_ROUND_UP(obj_desc->common_field.
    - bit_length, 8);
    + if (obj_desc->common_field.bit_length > 8) {
    + unsigned width =
    + ACPI_ROUND_BITS_UP_TO_BYTES(
    + obj_desc->common_field.bit_length);
    + // access_bit_width is u8, don't overflow it
    + if (width > 8)
    + width = 8;
    obj_desc->common_field.access_byte_width =
    - ACPI_DIV_8(obj_desc->common_field.
    - access_bit_width);
    + width;
    + obj_desc->common_field.access_bit_width =
    + 8 * width;
    + }
    }

    ACPI_DEBUG_PRINT((ACPI_DB_BFIELD,



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