From a93eac0e843148dc2d631c3ba80af17e9c8c860f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?F=C3=A1bio=20Cabral=20Pacheco?= <fcabralpacheco@gmail.com>
Date: Fri, 20 Dec 2019 12:03:33 -0300
Subject: [PATCH] Fix potential NULL pointer dereference in gdImageClone()

---
 src/gd.c                          |  9 +--------
 tests/gdimageclone/CMakeLists.txt |  1 +
 tests/gdimageclone/Makemodule.am  |  3 ++-
 tests/gdimageclone/style.c        | 30 ++++++++++++++++++++++++++++++
 5 files changed, 35 insertions(+), 9 deletions(-)
 create mode 100644 tests/gdimageclone/style.c

diff --git a/src/gd.c b/src/gd.c
index 592a0286..d564d1f9 100644
--- a/src/gd.c
+++ b/src/gd.c
@@ -2865,14 +2865,6 @@ BGD_DECLARE(gdImagePtr) gdImageClone (gdImagePtr src) {
 		}
 	}
 
-	if (src->styleLength > 0) {
-		dst->styleLength = src->styleLength;
-		dst->stylePos    = src->stylePos;
-		for (i = 0; i < src->styleLength; i++) {
-			dst->style[i] = src->style[i];
-		}
-	}
-
 	dst->interlace   = src->interlace;
 
 	dst->alphaBlendingFlag = src->alphaBlendingFlag;
@@ -2907,6 +2899,7 @@ BGD_DECLARE(gdImagePtr) gdImageClone (gdImagePtr src) {
 
 	if (src->style) {
 		gdImageSetStyle(dst, src->style, src->styleLength);
+		dst->stylePos = src->stylePos;
 	}
 
 	for (i = 0; i < gdMaxColors; i++) {
diff --git a/tests/gdimageclone/CMakeLists.txt b/tests/gdimageclone/CMakeLists.txt
index e6ccc318..662f4e96 100644
--- a/tests/gdimageclone/CMakeLists.txt
+++ b/tests/gdimageclone/CMakeLists.txt
@@ -1,5 +1,6 @@
 LIST(APPEND TESTS_FILES
 	bug00300
+	style
 )
 
 ADD_GD_TESTS()
diff --git a/tests/gdimageclone/Makemodule.am b/tests/gdimageclone/Makemodule.am
index 4b1b54c0..51abf5c1 100644
--- a/tests/gdimageclone/Makemodule.am
+++ b/tests/gdimageclone/Makemodule.am
@@ -1,5 +1,6 @@
 libgd_test_programs += \
-	gdimageclone/bug00300
+	gdimageclone/bug00300 \
+	gdimageclone/style
 
 EXTRA_DIST += \
 	gdimageclone/CMakeLists.txt
diff --git a/tests/gdimageclone/style.c b/tests/gdimageclone/style.c
new file mode 100644
index 00000000..c2b246ed
--- /dev/null
+++ b/tests/gdimageclone/style.c
@@ -0,0 +1,30 @@
+/**
+ * Cloning an image should exactly reproduce all style related data
+ */
+
+
+#include <string.h>
+#include "gd.h"
+#include "gdtest.h"
+
+
+int main()
+{
+    gdImagePtr im, clone;
+    int style[] = {0, 0, 0};
+
+    im = gdImageCreate(8, 8);
+    gdImageSetStyle(im, style, sizeof(style)/sizeof(style[0]));
+
+    clone = gdImageClone(im);
+    gdTestAssert(clone != NULL);
+
+    gdTestAssert(clone->styleLength == im->styleLength);
+    gdTestAssert(clone->stylePos == im->stylePos);
+    gdTestAssert(!memcmp(clone->style, im->style, sizeof(style)/sizeof(style[0])));
+
+    gdImageDestroy(clone);
+    gdImageDestroy(im);
+
+    return gdNumFailures();
+}