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Commit 2060c445 authored by Alexey Starikovskiy's avatar Alexey Starikovskiy Committed by Len Brown
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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: default avatarAlexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent dadf28a1

drivers/acpi/acpica/exprep.c

+11 −6
Original line number Diff line number Diff line
@@ -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,