From 99b7ef940e04cd273d03c5fa93bf182db2d7ce8d Mon Sep 17 00:00:00 2001
From: Stanislav Malyshev <stas@php.net>
Date: Sun, 7 Jul 2019 17:39:59 -0700
Subject: [PATCH] Fix bug #78256 (heap-buffer-overflow on
 exif_process_user_comment)

---
 ext/exif/exif.c              |  4 ++--
 ext/exif/tests/bug78256.phpt | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 ext/exif/tests/bug78256.phpt

diff --git a/ext/exif/exif.c b/ext/exif/exif.c
index 77a11300..a80f2c2a 100644
--- a/ext/exif/exif.c
+++ b/ext/exif/exif.c
@@ -3040,11 +3040,11 @@ static int exif_process_user_comment(image_info_type *ImageInfo, char **pszInfoP
 			/* First try to detect BOM: ZERO WIDTH NOBREAK SPACE (FEFF 16)
 			 * since we have no encoding support for the BOM yet we skip that.
 			 */
-			if (!memcmp(szValuePtr, "\xFE\xFF", 2)) {
+			if (ByteCount >=2 && !memcmp(szValuePtr, "\xFE\xFF", 2)) {
 				decode = "UCS-2BE";
 				szValuePtr = szValuePtr+2;
 				ByteCount -= 2;
-			} else if (!memcmp(szValuePtr, "\xFF\xFE", 2)) {
+			} else if (ByteCount >=2 && !memcmp(szValuePtr, "\xFF\xFE", 2)) {
 				decode = "UCS-2LE";
 				szValuePtr = szValuePtr+2;
 				ByteCount -= 2;
diff --git a/ext/exif/tests/bug78256.phpt b/ext/exif/tests/bug78256.phpt
new file mode 100644
index 00000000..37a3f1d8
--- /dev/null
+++ b/ext/exif/tests/bug78256.phpt
@@ -0,0 +1,11 @@
+--TEST--
+Bug #78256 (heap-buffer-overflow on exif_process_user_comment)
+--SKIPIF--
+<?php if (!extension_loaded('exif')) print 'skip exif extension not available';?>
+--FILE--
+<?php
+@exif_read_data(__DIR__."/bug78256.jpg", 'COMMENT', FALSE, TRUE);
+?>
+DONE
+--EXPECTF--
+DONE
\ No newline at end of file
-- 
2.21.0

