SECURITY: fix botched integer overflow handling logic in stralloc_ready (Giorgio)

CHANGES

@@ -28,6 +28,7 @@
     zero length buffer
   if SOCK_NONBLOCK is defined, use it instead of socket+fcntl
   ... but if errno==EINVAL still fall back to socket+fcntl (Robert Henney)
+  SECURITY: fix botched integer overflow handling logic in stralloc_ready (Giorgio)
 
 0.29:
   save 8 bytes in taia.h for 64-bit systems

stralloc/stralloc_ready.c

@@ -9,7 +9,8 @@
  * old space, and returns 1. Note that this changes sa.s. */
 int stralloc_ready(stralloc *sa,size_t len) {
   register size_t wanted=len+(len>>3)+30; /* heuristic from djb */
-  if (wanted<len || !sa->s || sa->a<len) {
+  if (wanted<len) wanted=len;
+  if (!sa->s || sa->a<len) {
     register char* tmp;
     if (!(tmp=realloc(sa->s,wanted)))
       return 0;