From 2060c44576c79086ff24718878d7edaa7384a985 Mon Sep 17 00:00:00 2001 From: Alexey Starikovskiy Date: Fri, 16 Apr 2010 15:36:40 -0400 Subject: [PATCH] ACPI: EC: Limit burst to 64 bits 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 Signed-off-by: Len Brown --- drivers/acpi/acpica/exprep.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/acpi/acpica/exprep.c b/drivers/acpi/acpica/exprep.c index a610ebe18edd..2fbfe51fb141 100644 --- a/drivers/acpi/acpica/exprep.c +++ b/drivers/acpi/acpica/exprep.c @@ -471,13 +471,18 @@ acpi_status acpi_ex_prep_field_value(struct acpi_create_field_info *info) /* 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,