Don't misinterpret DJI info maker note as DJI maker note

The DJI and DJI info maker note both share the "DJI" make string.
This caused the current code to try to interpret the DJI info maker note
as a DJI maker note. However, the DJI info maker note requires custom
parsing. Therefore, the misinterpretation actually caused the current
code to believe that there was an unrecoverable error in the IFD for the
maker note by returning false in the maker note parser. This in turn
caused the inability to parse other EXIF metadata.

This patch adds the identification of the DJI info maker note so that it
cannot be misinterpreted. Since we don't implement custom parsing, it
achieves this by setting the tag list to a special marker value (in this
case the NULL pointer). When this marker value is detected, the function
will just skip parsing the maker note and return true. Therefore, the
other code will believe that the IFD is not corrupt.

This approach is similar to handing an unrecognised maker note type
(see the loop on top of exif_process_IFD_in_MAKERNOTE() which also
returns true and treats it as a string). The end result of this patch
is that the DJI info maker note is considered as unknown to the caller of
exif_process_IFD_in_MAKERNOTE(), and therefore that the other EXIF
metadata can be parsed successfully.

Author: nielsdos

ext/exif/exif.c

@@ -1277,6 +1277,9 @@ typedef struct {
 	mn_offset_mode_t offset_mode;
 } maker_note_type;
 
+/* Some maker notes (e.g. DJI info tag) require custom parsing */
+#define REQUIRES_CUSTOM_PARSING NULL
+
 /* Remember to update PHP_MINFO if updated */
 static const maker_note_type maker_note_array[] = {
   { tag_table_VND_CANON,     "Canon",                   NULL,								0,  0,  MN_ORDER_INTEL,    MN_OFFSET_NORMAL},
@@ -1287,6 +1290,7 @@ static const maker_note_type maker_note_array[] = {
   { tag_table_VND_OLYMPUS,   "OLYMPUS OPTICAL CO.,LTD", "OLYMP\x00\x01\x00",				8,  8,  MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
   { tag_table_VND_SAMSUNG,   "SAMSUNG",                 NULL,								0,  0,  MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
   { tag_table_VND_PANASONIC, "Panasonic",               "Panasonic\x00\x00\x00",			12, 12, MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
+  { REQUIRES_CUSTOM_PARSING, "DJI",                     "[ae_dbg_info:",					13, 13, MN_ORDER_MOTOROLA, MN_OFFSET_NORMAL},
   { tag_table_VND_DJI,       "DJI",                     NULL,								0,  0,  MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
   { tag_table_VND_SONY,      "SONY",                    "SONY DSC \x00\x00\x00",			12, 12, MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
   { tag_table_VND_SONY,      "SONY",                    NULL,								0,  0,  MN_ORDER_NORMAL,   MN_OFFSET_NORMAL},
@@ -3168,6 +3172,12 @@ static bool exif_process_IFD_in_MAKERNOTE(image_info_type *ImageInfo, char * val
 		return true;
 	}
 
+	if (UNEXPECTED(maker_note->tag_table == REQUIRES_CUSTOM_PARSING)) {
+		/* Custom parsing required, which is not implemented at this point
+		 * Return true so that other metadata can still be parsed. */
+		return true;
+	}
+
 	dir_start = value_ptr + maker_note->offset;
 
 #ifdef EXIF_DEBUG