Might want to update the buffer pointer after a realloc (or we crash)

(closes issue #14485)
 Reported by: davevg


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@176360 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/strings.c

@@ -131,6 +131,7 @@ char *__ast_str_helper2(struct ast_str **buf, size_t maxlen, const char *src, si
 		(*buf)->__AST_STR_USED++;
 
 		if (dynamic && (!maxlen || (escapecommas && !(maxlen - 1)))) {
+			char *oldbase = (*buf)->__AST_STR_STR;
 			size_t old = (*buf)->__AST_STR_LEN;
 			if (ast_str_make_space(buf, (*buf)->__AST_STR_LEN * 2)) {
 				/* If the buffer can't be extended, end it. */
@@ -138,6 +139,11 @@ char *__ast_str_helper2(struct ast_str **buf, size_t maxlen, const char *src, si
 			}
 			/* What we extended the buffer by */
 			maxlen = old;
+
+			/* Update ptr, if necessary */
+			if ((*buf)->__AST_STR_STR != oldbase) {
+				ptr = ptr - oldbase + (*buf)->__AST_STR_STR;
+			}
 		}
 	}
 	if (__builtin_expect(!(maxsrc && maxlen), 0)) {