ACPICA: acpi_dmar_andd: Replace 1-element array with flexible array

ACPICA commit 3c19ae70424e9ab1e1b805203d300d2660f9a2f7

Similar to "Replace one-element array with flexible-array", replace the
1-element array with a proper flexible array member as defined by C99.

This allows the code to operate without tripping compile-time and run-
time bounds checkers (e.g. via __builtin_object_size(), -fsanitize=bounds,
and/or -fstrict-flex-arrays=3).

The handling of struct acpi_dmar_andd by acpi_dm_dump_dmar() appears to
expect a single trailing char for calculating table offsets. Keep a char
in the union to avoid any code changes appearing in the .text or .data
sections.

Link: acpica/acpica@3c19ae70
Signed-off-by: Kees Cook <kees@outflux.net>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: kees

include/acpi/actbl1.h

@@ -901,7 +901,10 @@ struct acpi_dmar_andd {
 	struct acpi_dmar_header header;
 	u8 reserved[3];
 	u8 device_number;
-	char device_name[1];
+	union {
+		char __pad;
+		 ACPI_FLEX_ARRAY(char, device_name);
+	};
 };
 
 /* 5: SOC Integrated Address Translation Cache Reporting Structure */