util: do not use stack frame for parsing arbitrary inputs

This replaces strndupa() by strndup() in socket_address_parse(),
as input string may be too long.

Fixes issue 10007 by ClusterFuzz-External:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=10007

src/basic/socket-util.c

@@ -50,7 +50,8 @@ static const char* const socket_address_type_table[] = {
 DEFINE_STRING_TABLE_LOOKUP(socket_address_type, int);
 
 int socket_address_parse(SocketAddress *a, const char *s) {
-        char *e, *n;
+        _cleanup_free_ char *n = NULL;
+        char *e;
         int r;
 
         assert(a);
@@ -68,7 +69,9 @@ int socket_address_parse(SocketAddress *a, const char *s) {
                 if (!e)
                         return -EINVAL;
 
-                n = strndupa(s+1, e-s-1);
+                n = strndup(s+1, e-s-1);
+                if (!n)
+                        return -ENOMEM;
 
                 errno = 0;
                 if (inet_pton(AF_INET6, n, &a->sockaddr.in6.sin6_addr) <= 0)
@@ -125,7 +128,10 @@ int socket_address_parse(SocketAddress *a, const char *s) {
                 if (r < 0)
                         return r;
 
-                n = strndupa(cid_start, e - cid_start);
+                n = strndup(cid_start, e - cid_start);
+                if (!n)
+                        return -ENOMEM;
+
                 if (!isempty(n)) {
                         r = safe_atou(n, &a->sockaddr.vm.svm_cid);
                         if (r < 0)
@@ -146,7 +152,9 @@ int socket_address_parse(SocketAddress *a, const char *s) {
                         if (r < 0)
                                 return r;
 
-                        n = strndupa(s, e-s);
+                        n = strndup(s, e-s);
+                        if (!n)
+                                return -ENOMEM;
 
                         /* IPv4 in w.x.y.z:p notation? */
                         r = inet_pton(AF_INET, n, &a->sockaddr.in.sin_addr);