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Bug 693284: Prevent read access violation. Check whether there's enough data.

--- a/jbig2_symbol_dict.c

+++ b/jbig2_symbol_dict.c

@@ -692,6 +692,13 @@

 		((image->width & 7) ? 1 : 0);

 	  byte *dst = image->data;

+	  /* SumatraPDF: prevent read access violation */

+	  if (size - jbig2_huffman_offset(hs) < image->height * stride) {

+	    jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number, "not enough data for decoding (%d/%d)", image->height * stride, size - jbig2_huffman_offset(hs));

+	    jbig2_image_release(ctx, image);

+	    goto cleanup4;

+	  }

+

 	  BMSIZE = image->height * stride;

 	  jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,

 	    "reading %dx%d uncompressed bitmap"

@@ -705,6 +712,13 @@

 	  }

 	} else {

 	  Jbig2GenericRegionParams rparams;

+

+	  /* SumatraPDF: prevent read access violation */

+	  if (size - jbig2_huffman_offset(hs) < BMSIZE) {

+	    jbig2_error(ctx, JBIG2_SEVERITY_FATAL, segment->number, "not enough data for decoding (%d/%d)", BMSIZE, size - jbig2_huffman_offset(hs));

+	    jbig2_image_release(ctx, image);

+	    goto cleanup4;

+	  }

 	  jbig2_error(ctx, JBIG2_SEVERITY_DEBUG, segment->number,

 	    "reading %dx%d collective bitmap for %d symbols (%d bytes)",