[PATCH 04/10] MdePkg/PiFirmwareFile: fix undefined behavior in FFS_FILE_SIZE

["Laszlo Ersek" <lersek@redhat.com>]

Accessing "EFI_FFS_FILE_HEADER.Size", which is of type UINT8[3], through a
(UINT32*), is undefined behavior. Fix it by accessing the array elements
individually.

(We can't use a union here, unfortunately, as easily as with
"EFI_COMMON_SECTION_HEADER", given the fields in "EFI_FFS_FILE_HEADER".)

Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=1710
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
---
 MdePkg/Include/Pi/PiFirmwareFile.h | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/MdePkg/Include/Pi/PiFirmwareFile.h b/MdePkg/Include/Pi/PiFirmwareFile.h
index 4fce8298d1c0..0668f3fa9af4 100644
--- a/MdePkg/Include/Pi/PiFirmwareFile.h
+++ b/MdePkg/Include/Pi/PiFirmwareFile.h
@@ -174,18 +174,26 @@ typedef struct {
   /// If FFS_ATTRIB_LARGE_FILE is not set then EFI_FFS_FILE_HEADER is used.
   ///
   UINT64                    ExtendedSize;
 } EFI_FFS_FILE_HEADER2;
 
 #define IS_FFS_FILE2(FfsFileHeaderPtr) \
     (((((EFI_FFS_FILE_HEADER *) (UINTN) FfsFileHeaderPtr)->Attributes) & FFS_ATTRIB_LARGE_FILE) == FFS_ATTRIB_LARGE_FILE)
 
+#define FFS_FILE_SIZE_ARRAY(FfsFileHeaderPtr) \
+    (((EFI_FFS_FILE_HEADER *) (UINTN) (FfsFileHeaderPtr))->Size)
+
+#define FFS_FILE_SIZE_ELEMENT(FfsFileHeaderPtr, Index) \
+    ((UINT32) FFS_FILE_SIZE_ARRAY (FfsFileHeaderPtr)[(Index)])
+
 #define FFS_FILE_SIZE(FfsFileHeaderPtr) \
-    ((UINT32) (*((UINT32 *) ((EFI_FFS_FILE_HEADER *) (UINTN) FfsFileHeaderPtr)->Size) & 0x00ffffff))
+    ((FFS_FILE_SIZE_ELEMENT ((FfsFileHeaderPtr), 0) <<  0) | \
+     (FFS_FILE_SIZE_ELEMENT ((FfsFileHeaderPtr), 1) <<  8) | \
+     (FFS_FILE_SIZE_ELEMENT ((FfsFileHeaderPtr), 2) << 16))
 
 #define FFS_FILE2_SIZE(FfsFileHeaderPtr) \
     ((UINT32) (((EFI_FFS_FILE_HEADER2 *) (UINTN) FfsFileHeaderPtr)->ExtendedSize))
 
 typedef UINT8 EFI_SECTION_TYPE;
 
 ///
 /// Pseudo type. It is used as a wild card when retrieving sections.
-- 
2.19.1.3.g30247aa5d201