Add reallocarray clone so we can stop doing multiply-then-reallocate

src/common/util.c

@@ -244,6 +244,20 @@ tor_realloc_(void *ptr, size_t size DMALLOC_PARAMS)
   return result;
 }
 
+/**
+ * Try to realloc <b>ptr</b> so that it takes up sz1 * sz2 bytes.  Check for
+ * overflow. Unlike other allocation functions, return NULL on overflow.
+ */
+void *
+tor_reallocarray_(void *ptr, size_t sz1, size_t sz2 DMALLOC_PARAMS)
+{
+  /* XXXX we can make this return 0, but we would need to check all the
+   * reallocarray users. */
+  tor_assert(sz2 == 0 || sz1 < SIZE_T_CEILING / sz2);
+
+  return tor_realloc(ptr, (sz1 * sz2) DMALLOC_FN_ARGS);
+}
+
 /** Return a newly allocated copy of the NUL-terminated string s. On
  * error, log and terminate.  (Like strdup(s), but never returns
  * NULL.)

src/common/util.h

@@ -79,6 +79,7 @@ void *tor_malloc_(size_t size DMALLOC_PARAMS) ATTR_MALLOC;
 void *tor_malloc_zero_(size_t size DMALLOC_PARAMS) ATTR_MALLOC;
 void *tor_calloc_(size_t nmemb, size_t size DMALLOC_PARAMS) ATTR_MALLOC;
 void *tor_realloc_(void *ptr, size_t size DMALLOC_PARAMS);
+void *tor_reallocarray_(void *ptr, size_t size1, size_t size2 DMALLOC_PARAMS);
 char *tor_strdup_(const char *s DMALLOC_PARAMS) ATTR_MALLOC ATTR_NONNULL((1));
 char *tor_strndup_(const char *s, size_t n DMALLOC_PARAMS)
   ATTR_MALLOC ATTR_NONNULL((1));
@@ -116,6 +117,8 @@ extern int dmalloc_free(const char *file, const int line, void *pnt,
 #define tor_malloc_zero(size)  tor_malloc_zero_(size DMALLOC_ARGS)
 #define tor_calloc(nmemb,size) tor_calloc_(nmemb, size DMALLOC_ARGS)
 #define tor_realloc(ptr, size) tor_realloc_(ptr, size DMALLOC_ARGS)
+#define tor_reallocarray(ptr, sz1, sz2) \
+  tor_reallocarray_((ptr), (sz1), (sz2) DMALLOC_ARGS)
 #define tor_strdup(s)          tor_strdup_(s DMALLOC_ARGS)
 #define tor_strndup(s, n)      tor_strndup_(s, n DMALLOC_ARGS)
 #define tor_memdup(s, n)       tor_memdup_(s, n DMALLOC_ARGS)