avcodec/utils: Fix potential overflow in overallocation code

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/utils.c

@@ -127,7 +127,7 @@ static inline int ff_fast_malloc(void *ptr, unsigned int *size, size_t min_size,
     void **p = ptr;
     if (min_size <= *size && *p)
         return 0;
-    min_size = FFMAX(17 * min_size / 16 + 32, min_size);
+    min_size = FFMAX(min_size + min_size / 16 + 32, min_size);
     av_free(*p);
     *p = zero_realloc ? av_mallocz(min_size) : av_malloc(min_size);
     if (!*p)