Harden a vestigial check against overflow inside `png_zalloc`
Reported-by: Sergio Atienza Pastor, MTP Métodos y Tecnología
diff --git a/png.c b/png.c
index d96c30a..673ddca 100644
--- a/png.c
+++ b/png.c
@@ -108,10 +108,16 @@
if (png_ptr == NULL)
return NULL;
- if (items >= (~(png_alloc_size_t)0)/size)
+ /* This check against overflow is vestigial, dating back from
+ * the old times when png_zalloc used to be an exported function.
+ * We're still keeping it here for now, as an extra-cautious
+ * prevention against programming errors inside zlib, although it
+ * should rather be a debug-time assertion instead.
+ */
+ if (size != 0 && items >= (~(png_alloc_size_t)0) / size)
{
- png_warning (png_voidcast(png_structrp, png_ptr),
- "Potential overflow in png_zalloc()");
+ png_warning(png_voidcast(png_structrp, png_ptr),
+ "Potential overflow in png_zalloc()");
return NULL;
}
