CVE-2019-6978: Double Free (CWE-415)
value: The GD Graphics Library (aka LibGD) 2.2.5 has a double free in the gdImage*Ptr() functions in gd_gif_out.c, gd_jpeg.c, and gd_wbmp.c. NOTE: PHP is unaffected.
CWE description: The product calls free() twice on the same memory address, potentially leading to modification of unexpected memory locations.
CVSS v3 base score: 9.8
Published: 2019-01-28T08:29Z
Repository: https://github.com/php/php-src
Language: C
Files changed: ext/gd/libgd/gd_gif_out.c, ext/gd/libgd/gd_jpeg.c, ext/gd/libgd/gd_wbmp.c
Commit date: 2019-01-19 11:30:12 +0100
Commit message: Sync with upstream

Even though libgd/libgd#492 is not a relevant bug fix for PHP, since
the binding doesn't use the `gdImage*Ptr()` functions at all, we're
porting the fix to stay in sync here.

Diff: diff --git a/ext/gd/libgd/gd_gif_out.c b/ext/gd/libgd/gd_gif_out.c
index 1f2a6b936a36..2e1f38af7047 100644
--- a/ext/gd/libgd/gd_gif_out.c
+++ b/ext/gd/libgd/gd_gif_out.c
@@ -95,16 +95,22 @@ static void output (code_int code, GifCtx *ctx);
 static void cl_block (GifCtx *ctx);
 static void cl_hash (register count_int chsize, GifCtx *ctx);
 static void char_init (GifCtx *ctx);
 static void char_out (int c, GifCtx *ctx);
 static void flush_char (GifCtx *ctx);
+
+static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out);
+
 void * gdImageGifPtr (gdImagePtr im, int *size)
 {
   void *rv;
   gdIOCtx *out = gdNewDynamicCtx (2048, NULL);
-  gdImageGifCtx (im, out);
-  rv = gdDPExtractData (out, size);
+	if (!_gdImageGifCtx(im, out)) {
+		rv = gdDPExtractData(out, size);
+	} else {
+		rv = NULL;
+	}
   out->gd_free (out);
   return rv;
 }
 
 void gdImageGif (gdImagePtr im, FILE * outFile)
@@ -113,21 +119,27 @@ void gdImageGif (gdImagePtr im, FILE * outFile)
   gdImageGifCtx (im, out);
   out->gd_free (out);
 }
 
 void gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
+{
+	_gdImageGifCtx(im, out);
+}
+
+/* returns 0 on success, 1 on failure */
+static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
 {
 	gdImagePtr pim = 0, tim = im;
 	int interlace, BitsPerPixel;
 	interlace = im->interlace;
 	if (im->trueColor) {
 		/* Expensive, but the only way that produces an
 			acceptable result: mix down to a palette
 			based temporary image. */
 		pim = gdImageCreatePaletteFromTrueColor(im, 1, 256);
 		if (!pim) {
-			return;
+			return 1;
 		}
 		tim = pim;
 	}
 	BitsPerPixel = colorstobpp(tim->colorsTotal);
 	/* All set, let's do it. */
@@ -136,10 +148,12 @@ void gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
 		tim->red, tim->green, tim->blue, tim);
 	if (pim) {
 		/* Destroy palette based temporary image. */
 		gdImageDestroy(	pim);
 	}
+
+    return 0;
 }
 
 static int
 colorstobpp(int colors)
 {
diff --git a/ext/gd/libgd/gd_jpeg.c b/ext/gd/libgd/gd_jpeg.c
index 8cf71fcbc9dd..ef46c4a22cf0 100644
--- a/ext/gd/libgd/gd_jpeg.c
+++ b/ext/gd/libgd/gd_jpeg.c
@@ -130,10 +130,11 @@ const char * gdJpegGetVersionString()
 		default:
 			return "unknown";
 	}
 }
 
+static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality);
 
 /*
  * Write IM to OUTFILE as a JFIF-formatted JPEG image, using quality
  * QUALITY.  If QUALITY is in the range 0-100, increasing values
  * represent higher quality but also larger image size.  If QUALITY is
@@ -151,20 +152,29 @@ void gdImageJpeg (gdImagePtr im, FILE * outFile, int quality)
 
 void *gdImageJpegPtr (gdImagePtr im, int *size, int quality)
 {
 	void *rv;
 	gdIOCtx *out = gdNewDynamicCtx (2048, NULL);
-	gdImageJpegCtx (im, out, quality);
-	rv = gdDPExtractData (out, size);
+	if (!_gdImageJpegCtx(im, out, quality)) {
+		rv = gdDPExtractData(out, size);
+	} else {
+		rv = NULL;
+	}
 	out->gd_free (out);
 
 	return rv;
 }
 
 void jpeg_gdIOCtx_dest (j_compress_ptr cinfo, gdIOCtx * outfile);
 
 void gdImageJpegCtx (gdImagePtr im, gdIOCtx * outfile, int quality)
+{
+	_gdImageJpegCtx(im, outfile, quality);
+}
+
+/* returns 0 on success, 1 on failure */
+static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)
 {
 	struct jpeg_compress_struct cinfo;
 	struct jpeg_error_mgr jerr;
 	int i, j, jidx;
 	/* volatile so we can gdFree it on return from longjmp */
@@ -182,11 +192,11 @@ void gdImageJpegCtx (gdImagePtr im, gdIOCtx * outfile, int quality)
 	if (setjmp (jmpbufw.jmpbuf) != 0) {
 		/* we're here courtesy of longjmp */
 		if (row) {
 			gdFree (row);
 		}
-		return;
+		return 1;
 	}
 
 	cinfo.err->error_exit = fatal_jpeg_error;
 
 	jpeg_create_compress (&cinfo);
@@ -275,10 +285,11 @@ void gdImageJpegCtx (gdImagePtr im, gdIOCtx * outfile, int quality)
 	}
 
 	jpeg_finish_compress (&cinfo);
 	jpeg_destroy_compress (&cinfo);
 	gdFree (row);
+	return 0;
 }
 
 gdImagePtr gdImageCreateFromJpeg (FILE * inFile)
 {
 	return gdImageCreateFromJpegEx(inFile, 1);
diff --git a/ext/gd/libgd/gd_wbmp.c b/ext/gd/libgd/gd_wbmp.c
index 55ced3443dea..fd9edad2cafa 100644
--- a/ext/gd/libgd/gd_wbmp.c
+++ b/ext/gd/libgd/gd_wbmp.c
@@ -80,10 +80,11 @@ void gd_putout (int i, void *out)
 int gd_getin (void *in)
 {
 	return (gdGetC((gdIOCtx *) in));
 }
 
+static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out);
 
 /*      gdImageWBMPCtx
    **  --------------
    **  Write the image as a wbmp file
    **  Parameters are:
@@ -91,18 +92,24 @@ int gd_getin (void *in)
    **  fg:     the index of the foreground color. any other value will be
    **          considered as background and will not be written
    **  out:    the stream where to write
  */
 void gdImageWBMPCtx (gdImagePtr image, int fg, gdIOCtx * out)
+{
+	_gdImageWBMPCtx(image, fg, out);
+}
+
+/* returns 0 on success, 1 on failure */
+static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)
 {
 	int x, y, pos;
 	Wbmp *wbmp;
 
 	/* create the WBMP */
 	if ((wbmp = createwbmp (gdImageSX (image), gdImageSY (image), WBMP_WHITE)) == NULL) {
 		gd_error("Could not create WBMP");
-		return;
+		return 1;
 	}
 
 	/* fill up the WBMP structure */
 	pos = 0;
 	for (y = 0; y < gdImageSY(image); y++) {
@@ -114,11 +121,13 @@ void gdImageWBMPCtx (gdImagePtr image, int fg, gdIOCtx * out)
 		}
 	}
 
 	/* write the WBMP to a gd file descriptor */
 	if (writewbmp (wbmp, &gd_putout, out)) {
+		freewbmp(wbmp);
 		gd_error("Could not save WBMP");
+		return 1;
 	}
 	/* des submitted this bugfix: gdFree the memory. */
 	freewbmp(wbmp);
 }
 
@@ -202,11 +211,14 @@ void gdImageWBMP (gdImagePtr im, int fg, FILE * outFile)
  */
 void * gdImageWBMPPtr (gdImagePtr im, int *size, int fg)
 {
 	void *rv;
 	gdIOCtx *out = gdNewDynamicCtx(2048, NULL);
-	gdImageWBMPCtx(im, fg, out);
-	rv = gdDPExtractData(out, size);
+	if (!_gdImageWBMPCtx(im, fg, out)) {
+		rv = gdDPExtractData(out, size);
+	} else {
+		rv = NULL;
+	}
 	out->gd_free(out);
 
 	return rv;
 }

Vulnerable code:   gdImageGifCtx (im, out);
  rv = gdDPExtractData (out, size);
			return;
	gdImageJpegCtx (im, out, quality);
	rv = gdDPExtractData (out, size);
		return;
		return;
	gdImageWBMPCtx(im, fg, out);
	rv = gdDPExtractData(out, size);
Fixed code: 
static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out);

	if (!_gdImageGifCtx(im, out)) {
		rv = gdDPExtractData(out, size);
	} else {
		rv = NULL;
	}
{
	_gdImageGifCtx(im, out);
}

/* returns 0 on success, 1 on failure */
static int _gdImageGifCtx(gdImagePtr im, gdIOCtxPtr out)
			return 1;

    return 0;
static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality);
	if (!_gdImageJpegCtx(im, out, quality)) {
		rv = gdDPExtractData(out, size);
	} else {
		rv = NULL;
	}
{
	_gdImageJpegCtx(im, outfile, quality);
}

/* returns 0 on success, 1 on failure */
static int _gdImageJpegCtx(gdImagePtr im, gdIOCtx *outfile, int quality)
		return 1;
	return 0;
static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out);
{
	_gdImageWBMPCtx(image, fg, out);
}

/* returns 0 on success, 1 on failure */
static int _gdImageWBMPCtx(gdImagePtr image, int fg, gdIOCtx *out)
		return 1;
		freewbmp(wbmp);
		return 1;
	if (!_gdImageWBMPCtx(im, fg, out)) {
		rv = gdDPExtractData(out, size);
	} else {
		rv = NULL;
	}