File bug-771229_CVE-2012-2836-2.patch of Package libexif.648

Update of /cvsroot/libexif/libexif/libexif
In directory vz-cvs-4.sog:/tmp/cvs-serv19533/libexif

Modified Files:
	exif-data.c 
Log Message:
Fix a buffer overflow on corrupted JPEG data
An unsigned data length might wrap around when decremented
below zero, bypassing sanity checks on length.
This code path can probably only occur if exif_data_load_data()
is called directly by the application on data that wasn't parsed
by libexif itself.
This solves the other part of CVE-2012-2836


Index: exif-data.c
===================================================================
RCS file: /cvsroot/libexif/libexif/libexif/exif-data.c,v
retrieving revision 1.130
retrieving revision 1.131
diff -u -d -r1.130 -r1.131
--- libexif/exif-data.c	12 Jul 2012 17:27:27 -0000	1.130
+++ libexif/exif-data.c	12 Jul 2012 17:28:26 -0000	1.131
@@ -807,21 +807,21 @@
 		exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
 			  "Found EXIF header.");
 	} else {
-		while (1) {
-			while ((d[0] == 0xff) && ds) {
+		while (ds >= 3) {
+			while (ds && (d[0] == 0xff)) {
 				d++;
 				ds--;
 			}
 
 			/* JPEG_MARKER_SOI */
-			if (d[0] == JPEG_MARKER_SOI) {
+			if (ds && d[0] == JPEG_MARKER_SOI) {
 				d++;
 				ds--;
 				continue;
 			}
 
 			/* JPEG_MARKER_APP0 */
-			if (d[0] == JPEG_MARKER_APP0) {
+			if (ds >= 3 && d[0] == JPEG_MARKER_APP0) {
 				d++;
 				ds--;
 				l = (d[0] << 8) | d[1];
@@ -833,7 +833,7 @@
 			}
 
 			/* JPEG_MARKER_APP1 */
-			if (d[0] == JPEG_MARKER_APP1)
+			if (ds && d[0] == JPEG_MARKER_APP1)
 				break;
 
 			/* Unknown marker or data. Give up. */
@@ -841,12 +841,12 @@
 				  "ExifData", _("EXIF marker not found."));
 			return;
 		}
-		d++;
-		ds--;
-		if (ds < 2) {
+		if (ds < 3) {
 			LOG_TOO_SMALL;
 			return;
 		}
+		d++;
+		ds--;
 		len = (d[0] << 8) | d[1];
 		exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
 			  "We have to deal with %i byte(s) of EXIF data.",


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