Fix bug #68601 buffer read overflow in gd_gif_in.c

remicollet · remicollet · commit 07b5896a1389 · 2014-12-13T09:03:44.000+01:00
diff --git a/ext/gd/libgd/gd_gif_in.c b/ext/gd/libgd/gd_gif_in.c
@@ -72,8 +72,10 @@ static struct {
 
 #define STACK_SIZE ((1<<(MAX_LWZ_BITS))*2)
 
+#define CSD_BUF_SIZE 280
+
 typedef struct {
-	unsigned char    buf[280];
+	unsigned char    buf[CSD_BUF_SIZE];
 	int              curbit, lastbit, done, last_byte;
 } CODE_STATIC_DATA;
 
@@ -400,7 +402,12 @@ GetCode_(gdIOCtx *fd, CODE_STATIC_DATA *scd, int code_size, int flag, int *ZeroD
 
 	ret = 0;
 	for (i = scd->curbit, j = 0; j < code_size; ++i, ++j)
-		ret |= ((scd->buf[ i / 8 ] & (1 << (i % 8))) != 0) << j;
+		if (i < CSD_BUF_SIZE * 8) {
+			ret |= ((scd->buf[i / 8] & (1 << (i % 8))) != 0) << j;
+		} else {
+			ret = -1;
+			break;
+		}
 
 	scd->curbit += code_size;
 	return ret;
