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 <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/drivers/acpi/acpica/exprep.c b/drivers/acpi/acpica/exprep.c
index a610ebe..2fbfe51 100644 (file)
--- 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,