net: avoid closing NULL socket in DNS lookup

Refactor code so that we do not store NULL pointers in array
of in-flight DNS servers.

Reported-By: Josef Bacik <jbacik@fb.com>

diff --git a/grub-core/net/dns.c b/grub-core/net/dns.c
index 9d0c8fcea60b671debcd7e04978f07b76f8654f9..953f3bedd9d9725c9fd2a3963766c0f899743aa0 100644 (file)
--- a/grub-core/net/dns.c
+++ b/grub-core/net/dns.c
@@ -437,7 +437,7 @@ grub_net_dns_lookup (const char *name,
   struct recv_data data = {naddresses, addresses, cache,
                           grub_cpu_to_be16 (id++), 0, 0, name, 0};
   grub_uint8_t *nbd;
-  int have_server = 0;
+  grub_size_t try_server = 0;
 
   if (!servers)
     {
@@ -543,33 +543,31 @@ grub_net_dns_lookup (const char *name,
   for (i = 0; i < n_servers * 4; i++)
     {
       /* Connect to a next server.  */
-      while (!(i & 1) && send_servers < n_servers)
+      while (!(i & 1) && try_server < n_servers)
        {
-         sockets[send_servers] = grub_net_udp_open (servers[send_servers],
+         sockets[send_servers] = grub_net_udp_open (servers[try_server++],
                                                     DNS_PORT,
                                                     recv_hook,
                                                     &data);
-         send_servers++;
-         if (!sockets[send_servers - 1])
+         if (!sockets[send_servers])
            {
              err = grub_errno;
              grub_errno = GRUB_ERR_NONE;
            }
          else
            {
-             have_server = 1;
+             send_servers++;
              break;
            }
        }
-      if (!have_server)
+      if (!send_servers)
        goto out;
       if (*data.naddresses)
        goto out;
       for (j = 0; j < send_servers; j++)
        {
           grub_err_t err2;
-          if (!sockets[j])
-            continue;
+
           nb->data = nbd;
 
           grub_size_t t = 0;