lxccontainer: fix mount api (mount_injection_file)

src/lxc/api_extensions.h

@@ -40,6 +40,7 @@ static char *api_extensions[] = {
 	"reboot2",
 	"mount_injection",
 	"cgroup_relative",
+	"mount_injection_file",
 };
 
 static size_t nr_api_extensions = sizeof(api_extensions) / sizeof(*api_extensions);

src/lxc/lxccontainer.c

@@ -5045,10 +5045,13 @@ static int do_lxcapi_mount(struct lxc_container *c, const char *source,
 
 		/* Enter the container namespaces */
 		if (!lxc_list_empty(&c->lxc_conf->id_map)) {
-			if (!switch_to_ns(init_pid, "user")){
+			if (!switch_to_ns(init_pid, "user")) {
 				ERROR("Failed to enter user namespace");
 				_exit(EXIT_FAILURE);
 			}
+
+			if (!lxc_switch_uid_gid(0, 0))
+				_exit(EXIT_FAILURE);
 		}
 
 		if (!switch_to_ns(init_pid, "mnt")) {