From 8058989645e9fdb0dd13a369c2e2899016d70533 Mon Sep 17 00:00:00 2001
From: Christian Grothoff <christian@grothoff.org>
Date: Fri, 5 Jan 2018 20:53:20 +0100
Subject: fix potential use after free in tcp

---
 src/transport/tcp_connection_legacy.c |  9 ++++++---
 src/transport/tcp_server_legacy.c     | 24 ++++++++++++++----------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/src/transport/tcp_connection_legacy.c b/src/transport/tcp_connection_legacy.c
index 5b219a467..17157436d 100644
--- a/src/transport/tcp_connection_legacy.c
+++ b/src/transport/tcp_connection_legacy.c
@@ -1218,8 +1218,10 @@ RETRY:
  * @param timeout maximum amount of time to wait
  * @param receiver function to call with received data
  * @param receiver_cls closure for @a receiver
+ * @return #GNUNET_SYSERR if @a connection died (receiver was
+ *          called with error)
  */
-void
+int
 GNUNET_CONNECTION_receive (struct GNUNET_CONNECTION_Handle *connection,
                            size_t max,
                            struct GNUNET_TIME_Relative timeout,
@@ -1241,7 +1243,7 @@ GNUNET_CONNECTION_receive (struct GNUNET_CONNECTION_Handle *connection,
                                      connection->sock,
                                      &receive_ready,
                                      connection);
-    return;
+    return GNUNET_OK;
   }
   if ((NULL == connection->dns_active) &&
       (NULL == connection->ap_head) &&
@@ -1252,8 +1254,9 @@ GNUNET_CONNECTION_receive (struct GNUNET_CONNECTION_Handle *connection,
 	      NULL, 0,
 	      NULL, 0,
 	      ETIMEDOUT);
-    return;
+    return GNUNET_SYSERR;
   }
+  return GNUNET_OK;
 }
 
 
diff --git a/src/transport/tcp_server_legacy.c b/src/transport/tcp_server_legacy.c
index d0ce790fc..f75b41e8c 100644
--- a/src/transport/tcp_server_legacy.c
+++ b/src/transport/tcp_server_legacy.c
@@ -1044,11 +1044,13 @@ process_mst (struct GNUNET_SERVER_Client *client,
            "Server re-enters receive loop, timeout: %s.\n",
            GNUNET_STRINGS_relative_time_to_string (client->idle_timeout, GNUNET_YES));
       client->receive_pending = GNUNET_YES;
-      GNUNET_CONNECTION_receive (client->connection,
-                                 GNUNET_MAX_MESSAGE_SIZE - 1,
-                                 client->idle_timeout,
-                                 &process_incoming,
-                                 client);
+      if (GNUNET_OK !=
+	  GNUNET_CONNECTION_receive (client->connection,
+				     GNUNET_MAX_MESSAGE_SIZE - 1,
+				     client->idle_timeout,
+				     &process_incoming,
+				     client))
+	return;
       break;
     }
     LOG (GNUNET_ERROR_TYPE_DEBUG,
@@ -1287,11 +1289,13 @@ GNUNET_SERVER_connect_socket (struct GNUNET_SERVER_Handle *server,
   for (n = server->connect_notify_list_head; NULL != n; n = n->next)
     n->callback (n->callback_cls, client);
   client->receive_pending = GNUNET_YES;
-  GNUNET_CONNECTION_receive (client->connection,
-                             GNUNET_MAX_MESSAGE_SIZE - 1,
-                             client->idle_timeout,
-                             &process_incoming,
-                             client);
+  if (GNUNET_SYSERR ==
+      GNUNET_CONNECTION_receive (client->connection,
+				 GNUNET_MAX_MESSAGE_SIZE - 1,
+				 client->idle_timeout,
+				 &process_incoming,
+				 client))
+    return NULL;
   return client;
 }
 
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