ACPICA: Load operator: re-instate most restrictions on incoming table signature

Now, only allow "SSDT" "OEM", and a null signature.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/acpica/tbinstal.c

@@ -126,12 +126,29 @@ acpi_tb_add_table(struct acpi_table_desc *table_desc, u32 *table_index)
 	}
 
 	/*
-	 * Originally, we checked the table signature for "SSDT" or "PSDT" here.
-	 * Next, we added support for OEMx tables, signature "OEM".
-	 * Valid tables were encountered with a null signature, so we've just
-	 * given up on validating the signature, since it seems to be a waste
-	 * of code. The original code was removed (05/2008).
+	 * Validate the incoming table signature.
+	 *
+	 * 1) Originally, we checked the table signature for "SSDT" or "PSDT".
+	 * 2) We added support for OEMx tables, signature "OEM".
+	 * 3) Valid tables were encountered with a null signature, so we just
+	 *    gave up on validating the signature, (05/2008).
+	 * 4) We encountered non-AML tables such as the MADT, which caused
+	 *    interpreter errors and kernel faults. So now, we once again allow
+	 *    only "SSDT", "OEMx", and now, also a null signature. (05/2011).
 	 */
+	if ((table_desc->pointer->signature[0] != 0x00) &&
+	    (!ACPI_COMPARE_NAME(table_desc->pointer->signature, ACPI_SIG_SSDT))
+	    && (ACPI_STRNCMP(table_desc->pointer->signature, "OEM", 3))) {
+		ACPI_ERROR((AE_INFO,
+			    "Table has invalid signature [%4.4s] (0x%8.8X), must be SSDT or OEMx",
+			    acpi_ut_valid_acpi_name(*(u32 *)table_desc->
+						    pointer->
+						    signature) ? table_desc->
+			    pointer->signature : "????",
+			    *(u32 *)table_desc->pointer->signature));
+
+		return_ACPI_STATUS(AE_BAD_SIGNATURE);
+	}
 
 	(void)acpi_ut_acquire_mutex(ACPI_MTX_TABLES);