ACPI_DMAR_ANDD: Replace 1-element array with flexible array

Similar to commit 7ba2f3d91a32 ("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 ACPI_DMAR_ANDD by AcpiDmDumpDmar() 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.

Signed-off-by: Kees Cook <kees@outflux.net>

1 files changed, 4 insertions, 1 deletions

diff --git a/source/include/actbl1.h b/source/include/actbl1.h
index 63f137117..cecd7edbe 100644
--- a/source/include/actbl1.h
+++ b/source/include/actbl1.h
@@ -1219,7 +1219,10 @@ typedef struct acpi_dmar_andd
     ACPI_DMAR_HEADER        Header;
     UINT8                   Reserved[3];
     UINT8                   DeviceNumber;
-    char                    DeviceName[1];
+    union {
+        char                  __pad;
+        ACPI_FLEX_ARRAY(char, DeviceName);
+    };
 
 } ACPI_DMAR_ANDD;