libexif: exif_data_load_data_content() should not recurse with the same offset.

libexif/exif-data.c

 /* exif-data.c
  *
  * Copyright (c) 2001 Lutz Mueller <lutz@users.sourceforge.net>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 346 matching lines @@
 static void
 exif_data_load_data_content (ExifData *data, ExifIfd ifd,
                              const unsigned char *d,
                              unsigned int ds, unsigned int offset, unsigned int recursion_depth)
 {
         ExifLong o, thumbnail_offset = 0, thumbnail_length = 0;
         ExifShort n;
         ExifEntry *entry;
         unsigned int i;
         ExifTag tag;
+        const unsigned int original_offset = offset;
 
         if (!data || !data->priv) 
                 return;
 
         /* check for valid ExifIfd enum range */
         if ((((int)ifd) < 0) || ( ((int)ifd) >= EXIF_IFD_COUNT))
           return;
 
         if (recursion_depth > 30) {
                 exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData",
@@ skipping 32 matching lines @@
                                            data->priv->order);
                         /* FIXME: IFD_POINTER tags aren't marked as being in a
                          * specific IFD, so exif_tag_get_name_in_ifd won't work
                          */
                         exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                   "Sub-IFD entry 0x%x ('%s') at %u.", tag,
                                   exif_tag_get_name(tag), o);
                         switch (tag) {
                         case EXIF_TAG_EXIF_IFD_POINTER:
                                 CHECK_REC (EXIF_IFD_EXIF);
+                                if (o == original_offset)
+                                        return;
                                 exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o, recursion_depth + 1);
                                 break;
                         case EXIF_TAG_GPS_INFO_IFD_POINTER:
                                 CHECK_REC (EXIF_IFD_GPS);
+                                if (o == original_offset)
+                                        return;
                                 exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o, recursion_depth + 1);
                                 break;
                         case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
                                 CHECK_REC (EXIF_IFD_INTEROPERABILITY);
+                                if (o == original_offset)
+                                        return;
                                 exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o, recursion_depth + 1);
                                 break;
                         case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
                                 thumbnail_offset = o;
                                 if (thumbnail_offset && thumbnail_length)
                                         exif_data_load_data_thumbnail (data, d,
                                                                        ds, thumbnail_offset,
                                                                        thumbnail_length);
                                 break;
                         case EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH:
@@ skipping 830 matching lines @@
                 return;
 
         d->priv->data_type = dt;
 }
 
 ExifDataType
 exif_data_get_data_type (ExifData *d)
 {
         return (d && d->priv) ? d->priv->data_type : EXIF_DATA_TYPE_UNKNOWN;
 }