Fix: event notifier group: fix fd leak on error

Use a regular pattern for all commands:

If the command callback takes ownership of a pointer or file descriptor,
it sets them to NULL or -1. Therefore, the caller can always try to free
the pointer, or close it if it is greater or equal to 0.

This eliminates memory and fd leaks on error.

Change-Id: If5181a0c438f2e1ac73e5d4d63d5cde21cc97e52
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

diff --git a/liblttng-ust/lttng-ust-abi.c b/liblttng-ust/lttng-ust-abi.c
index 77bb90db02d24d42ccdf6c996a3d1c82e9266e70..7490f8b72d22f28435a63475e3900953892d74b8 100644 (file)
--- a/liblttng-ust/lttng-ust-abi.c
+++ b/liblttng-ust/lttng-ust-abi.c
@@ -346,10 +346,10 @@ long lttng_abi_tracer_version(int objd,
 }
 
 static
-int lttng_abi_event_notifier_send_fd(void *owner, int event_notifier_notif_fd)
+int lttng_abi_event_notifier_send_fd(void *owner, int *event_notifier_notif_fd)
 {
        struct lttng_event_notifier_group *event_notifier_group;
-       int event_notifier_group_objd, ret, fd_flag, close_ret;
+       int event_notifier_group_objd, ret, fd_flag;
 
        event_notifier_group = lttng_event_notifier_group_create();
        if (!event_notifier_group)
@@ -358,11 +358,11 @@ int lttng_abi_event_notifier_send_fd(void *owner, int event_notifier_notif_fd)
        /*
         * Set this file descriptor as NON-BLOCKING.
         */
-       fd_flag = fcntl(event_notifier_notif_fd, F_GETFL);
+       fd_flag = fcntl(*event_notifier_notif_fd, F_GETFL);
 
        fd_flag |= O_NONBLOCK;
 
-       ret = fcntl(event_notifier_notif_fd, F_SETFL, fd_flag);
+       ret = fcntl(*event_notifier_notif_fd, F_SETFL, fd_flag);
        if (ret) {
                ret = -errno;
                goto fd_error;
@@ -377,18 +377,15 @@ int lttng_abi_event_notifier_send_fd(void *owner, int event_notifier_notif_fd)
 
        event_notifier_group->objd = event_notifier_group_objd;
        event_notifier_group->owner = owner;
-       event_notifier_group->notification_fd = event_notifier_notif_fd;
+       event_notifier_group->notification_fd = *event_notifier_notif_fd;
+       /* Object descriptor takes ownership of notification fd. */
+       *event_notifier_notif_fd = -1;
 
        return event_notifier_group_objd;
 
 objd_error:
        lttng_event_notifier_group_destroy(event_notifier_group);
 fd_error:
-       close_ret = close(event_notifier_notif_fd);
-       if (close_ret) {
-               PERROR("close");
-       }
-
        return ret;
 }
 
@@ -443,7 +440,7 @@ long lttng_cmd(int objd, unsigned int cmd, unsigned long arg,
                return 0;
        case LTTNG_UST_EVENT_NOTIFIER_GROUP_CREATE:
                return lttng_abi_event_notifier_send_fd(owner,
-                       uargs->event_notifier_handle.event_notifier_notif_fd);
+                       &uargs->event_notifier_handle.event_notifier_notif_fd);
        default:
                return -EINVAL;
        }

diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index 708b9192f22b62b14985f8d7ffa3c7d423813d2d..7e3bf45036d6f28741a337bd4d9004d3ae192b80 100644 (file)
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -987,7 +987,7 @@ int handle_message(struct sock_info *sock_info,
        }
        case LTTNG_UST_EVENT_NOTIFIER_GROUP_CREATE:
        {
-               int event_notifier_notif_fd;
+               int event_notifier_notif_fd, close_ret;
 
                len = ustcomm_recv_event_notifier_notif_fd_from_sessiond(sock,
                        &event_notifier_notif_fd);
@@ -1024,6 +1024,13 @@ int handle_message(struct sock_info *sock_info,
                                        &args, sock_info);
                else
                        ret = -ENOSYS;
+               if (args.event_notifier_handle.event_notifier_notif_fd >= 0) {
+                       lttng_ust_lock_fd_tracker();
+                       close_ret = close(args.event_notifier_handle.event_notifier_notif_fd);
+                       lttng_ust_unlock_fd_tracker();
+                       if (close_ret)
+                               PERROR("close");
+               }
                break;
        }
        case LTTNG_UST_CHANNEL: