Backported of:

From 9266d14b5ca4e29b970fa03272318e5f99386e06 Mon Sep 17 00:00:00 2001
From: Marcus Meissner <marcus@jet.franken.de>
Date: Thu, 5 Nov 2020 09:50:08 +0100
Subject: [PATCH] fixed a incorrect overflow check that could be optimized
 away.

inspired by:
https://android.googlesource.com/platform/external/libexif/+/8e7345f3bc0bad06ac369d6cbc1124c8ceaf7d4b

https://source.android.com/security/bulletin/2020-11-01

CVE-2020-0452
Index: libexif-0.6.21/libexif/exif-entry.c
===================================================================
--- libexif-0.6.21.orig/libexif/exif-entry.c
+++ libexif-0.6.21/libexif/exif-entry.c
@@ -28,6 +28,7 @@
 #include <ctype.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <stdint.h>
 #include <string.h>
 #include <time.h>
 #include <math.h>
@@ -1376,8 +1377,8 @@ exif_entry_get_value (ExifEntry *e, char
 	case EXIF_TAG_XP_KEYWORDS:
 	case EXIF_TAG_XP_SUBJECT:
 	{
-		/* Sanity check the size to prevent overflow */
-		if (e->size+sizeof(unsigned short) < e->size) break;
+		/* Sanity check the size to prevent overflow. Note EXIF files are 64kb at most. */
+		if (e->size >= 65536 - sizeof(uint16_t)*2) break;
 
 		/* The tag may not be U+0000-terminated , so make a local
 		   U+0000-terminated copy before converting it */