qemu-nbd: Fix a memleak in nbd_client_thread()

When the qio_channel_socket_connect_sync() fails
we should goto 'out_socket' label to free the 'sioc' instead of
goto 'out' label.
In addition, there's a lot of redundant code in the successful branch
and the error branch, optimize it.

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Alex Chen <alex.chen@huawei.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20201208134944.27962-1-alex.chen@huawei.com>

qemu-nbd.c

@@ -265,8 +265,8 @@ static void *nbd_client_thread(void *arg)
     char *device = arg;
     NBDExportInfo info = { .request_sizes = false, .name = g_strdup("") };
     QIOChannelSocket *sioc;
-    int fd;
-    int ret;
+    int fd = -1;
+    int ret = EXIT_FAILURE;
     pthread_t show_parts_thread;
     Error *local_error = NULL;
 
@@ -278,26 +278,24 @@ static void *nbd_client_thread(void *arg)
         goto out;
     }
 
-    ret = nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
-                                NULL, NULL, NULL, &info, &local_error);
-    if (ret < 0) {
+    if (nbd_receive_negotiate(NULL, QIO_CHANNEL(sioc),
+                              NULL, NULL, NULL, &info, &local_error) < 0) {
         if (local_error) {
             error_report_err(local_error);
         }
-        goto out_socket;
+        goto out;
     }
 
     fd = open(device, O_RDWR);
     if (fd < 0) {
         /* Linux-only, we can use %m in printf.  */
         error_report("Failed to open %s: %m", device);
-        goto out_socket;
+        goto out;
     }
 
-    ret = nbd_init(fd, sioc, &info, &local_error);
-    if (ret < 0) {
+    if (nbd_init(fd, sioc, &info, &local_error) < 0) {
         error_report_err(local_error);
-        goto out_fd;
+        goto out;
     }
 
     /* update partition table */
@@ -311,24 +309,20 @@ static void *nbd_client_thread(void *arg)
         dup2(STDOUT_FILENO, STDERR_FILENO);
     }
 
-    ret = nbd_client(fd);
-    if (ret) {
-        goto out_fd;
+    if (nbd_client(fd) < 0) {
+        goto out;
     }
-    close(fd);
-    object_unref(OBJECT(sioc));
-    g_free(info.name);
-    kill(getpid(), SIGTERM);
-    return (void *) EXIT_SUCCESS;
 
-out_fd:
-    close(fd);
-out_socket:
+    ret = EXIT_SUCCESS;
+
+ out:
+    if (fd >= 0) {
+        close(fd);
+    }
     object_unref(OBJECT(sioc));
-out:
     g_free(info.name);
     kill(getpid(), SIGTERM);
-    return (void *) EXIT_FAILURE;
+    return (void *) (intptr_t) ret;
 }
 #endif /* HAVE_NBD_DEVICE */