libreboot-utils: extremely safe(ish) malloc usage

yes, a common thing in C programs is one or all
of the following:

* use after frees
* double free (on non-NULL pointer)
* over-writing currently used pointer (mem leak)

i try to reduce the chance of this in my software,
by running free() through a filter function,
free_if_not_null, that returns if a function
is being freed twice - because it sets NULL
after freeing, but will only free if it's not
null already.

this patch adds two functions: smalloc and vmalloc,
for strings and voids. using these makes the program
abort if:

* non-null pointer given for initialisation
* pointer to pointer is null (of course)
* size of zero given, for malloc (zero bytes)

i myself was caught out by this change, prompting
me to make the following fix in fs_dirname_basename()
inside lib/file.c:

-       char *buf;
+       char *buf = NULL;

Yes.

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/libreboot-utils/lib/rand.c

@@ -72,13 +72,6 @@
  * or your program dies.
  */
 
-void *
-rmalloc(size_t *rval)
-{
-	return if_err(rval == NULL, EFAULT) ?
-	    NULL : mkrstr(*rval = rsize(BUFSIZ));
-}
-
 size_t
 rsize(size_t n)
 {
@@ -120,17 +113,7 @@ void *
 mkrbuf(size_t n)
 {
 	void *buf = NULL;
-
-	if (n == 0)
-		err_no_cleanup(0, EPERM, "mkrbuf: zero-byte request");
-
-	if (n >= SIZE_MAX - 1)
-		err_no_cleanup(0, EOVERFLOW, "integer overflow in mkrbuf");
-
-	if ((buf = malloc(n)) == NULL)
-		err_no_cleanup(0, ENOMEM, "mkrbuf: malloc");
-
-	rset(buf, n);
+	rset(vmalloc(&buf, n), n);
 	return buf; /* basically malloc() but with rand */
 }