Ensure sockets are kept open across all their hash table life-span

Otherwise causes races where re-use of a socket is being incorrectly
removed.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/lttng-sessiond/ust-app.c b/lttng-sessiond/ust-app.c
index 2bee4d90ab7626b7b51c314b67ef539d65441634..46c3dfdc12442247274801d26a3dac72f58bbf95 100644 (file)
--- a/lttng-sessiond/ust-app.c
+++ b/lttng-sessiond/ust-app.c
@@ -143,6 +143,7 @@ static void delete_ust_app(struct ust_app *app)
        struct cds_lfht_node *node;
        struct cds_lfht_iter iter;
        struct ust_app_session *ua_sess;
+       int sock;
 
        rcu_read_lock();
 
@@ -167,9 +168,8 @@ static void delete_ust_app(struct ust_app *app)
        /* Socket is already closed at this point */
 
        /* Delete ust app sessions info */
-       if (app->sock_closed) {
-               app->key.sock = -1;
-       }
+       sock = app->key.sock;
+       app->key.sock = -1;
 
        cds_lfht_for_each_entry(app->sessions, &iter, ua_sess, node) {
                hashtable_del(app->sessions, &iter);
@@ -182,9 +182,13 @@ static void delete_ust_app(struct ust_app *app)
                goto end;
        }
 
-       if (!app->sock_closed) {
-               close(app->key.sock);
-       }
+       /*
+        * Wait until we have removed the key from the sock hash table
+        * before closing this socket, otherwise an application could
+        * re-use the socket ID and race with the teardown, using the
+        * same hash table entry.
+        */
+       close(sock);
 
        DBG2("UST app pid %d deleted", app->key.pid);
        free(app);
@@ -881,10 +885,6 @@ void ust_app_unregister(int sock)
                goto error;
        }
 
-       /* We got called because the socket was closed on the remote end. */
-       close(sock);
-       /* Using a flag because we still need "sock" as a key. */
-       lta->sock_closed = 1;
        hashtable_del(ust_app_ht, &iter);
        call_rcu(&node->head, delete_ust_app_rcu);
 error:
@@ -983,8 +983,6 @@ void ust_app_clean_list(void)
 
        cds_lfht_for_each(ust_app_ht, &iter, node) {
                app = caa_container_of(node, struct ust_app, node);
-               close(app->key.sock);
-               app->sock_closed = 1;
 
                ret = hashtable_del(ust_app_ht, &iter);
                if (!ret) {

diff --git a/lttng-sessiond/ust-app.h b/lttng-sessiond/ust-app.h
index c730cb738044d7daf3a4f517ca570613a20dde0f..f8b0c6c6db604ff12d07e3b1307e3a901057130b 100644 (file)
--- a/lttng-sessiond/ust-app.h
+++ b/lttng-sessiond/ust-app.h
@@ -101,7 +101,6 @@ struct ust_app {
        struct cds_lfht *sessions;
        struct cds_lfht_node node;
        struct ust_app_key key;
-       int sock_closed;
 };
 
 #ifdef HAVE_LIBLTTNG_UST_CTL