ACPICA: Fix possible buffer overflow during a field unit read operation

Can only happen under these conditions: 1) The DSDT version is 1,
meaning integers are 32-bits.  2) The field is between 33 and 64
bits long.

It applies cleanly back to ACPICA 20100806+ (Linux v2.6.37+).

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Cc: 2.6.37+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/acpica/exfldio.c b/drivers/acpi/acpica/exfldio.c
index ec7f5690031b0c5c3c0e1b097f03943b3e07f510..c84ee956fa4c58f50c8849cc660a151d46febe39 100644 (file)
--- a/drivers/acpi/acpica/exfldio.c
+++ b/drivers/acpi/acpica/exfldio.c
@@ -720,7 +720,19 @@ acpi_ex_extract_from_field(union acpi_operand_object *obj_desc,
 
        if ((obj_desc->common_field.start_field_bit_offset == 0) &&
            (obj_desc->common_field.bit_length == access_bit_width)) {
-               status = acpi_ex_field_datum_io(obj_desc, 0, buffer, ACPI_READ);
+               if (buffer_length >= sizeof(u64)) {
+                       status =
+                           acpi_ex_field_datum_io(obj_desc, 0, buffer,
+                                                  ACPI_READ);
+               } else {
+                       /* Use raw_datum (u64) to handle buffers < 64 bits */
+
+                       status =
+                           acpi_ex_field_datum_io(obj_desc, 0, &raw_datum,
+                                                  ACPI_READ);
+                       ACPI_MEMCPY(buffer, &raw_datum, buffer_length);
+               }
+
                return_ACPI_STATUS(status);
        }