conf, lxccontainer: fix length checks in snprintf

src/lxc/conf.c

@@ -650,19 +650,13 @@ unsigned long add_required_remount_flags(const char *s, const char *d,
 
 static int add_shmount_to_list(struct lxc_conf *conf) {
 	char new_mount[MAXPATHLEN];
-	size_t len_mount;
 	/* Offset for the leading '/' since the path_cont
 	 * is absolute inside the container */
 	int ret = -1, offset = 1;
 
-	/* +1 for the separating whitespace */
-	len_mount = strlen(conf->shmount.path_host) + 1
-			+ strlen(conf->shmount.path_cont) - offset
-			+ sizeof(" none bind,create=dir 0 0") - 1;
-
-	ret = snprintf(new_mount, len_mount + 1, "%s %s none bind,create=dir 0 0",
+	ret = snprintf(new_mount, sizeof(new_mount), "%s %s none bind,create=dir 0 0",
 				   conf->shmount.path_host, conf->shmount.path_cont + offset);
-	if (ret < 0 || (size_t)ret >= len_mount + 1)
+	if (ret < 0 || (size_t)ret >= sizeof(new_mount))
 		return -1;
 
 	ret = add_elem_to_mount_list(new_mount, conf);

src/lxc/lxccontainer.c

@@ -4955,7 +4955,6 @@ static int do_lxcapi_mount(struct lxc_container *c, const char *source,
 			   struct lxc_mount *mnt)
 {
 	char *suff, *sret;
-	size_t len;
 	char template[MAXPATHLEN], path[MAXPATHLEN];
 	pid_t pid, init_pid;
 	struct stat sb;
@@ -4970,10 +4969,9 @@ static int do_lxcapi_mount(struct lxc_container *c, const char *source,
 		ERROR("Host path to shared mountpoint must be specified in the config\n");
 		return -EINVAL;
 	}
-	len = strlen(c->lxc_conf->shmount.path_host) + sizeof("/.lxcmount_XXXXXX") - 1;
 
-	ret = snprintf(template, len + 1, "%s/.lxcmount_XXXXXX", c->lxc_conf->shmount.path_host);
-	if (ret < 0 || (size_t)ret >= len + 1) {
+	ret = snprintf(template, sizeof(template), "%s/.lxcmount_XXXXXX", c->lxc_conf->shmount.path_host);
+	if (ret < 0 || (size_t)ret >= sizeof(template)) {
 		SYSERROR("Error writing shmounts tempdir name");
 		goto out;
 	}
@@ -5048,9 +5046,8 @@ static int do_lxcapi_mount(struct lxc_container *c, const char *source,
 		if (!suff)
 			_exit(EXIT_FAILURE);
 
-		len = strlen(c->lxc_conf->shmount.path_cont) + sizeof("/.lxcmount_XXXXXX") - 1;
-		ret = snprintf(path, len + 1, "%s%s", c->lxc_conf->shmount.path_cont, suff);
-		if (ret < 0 || (size_t)ret >= len + 1) {
+		ret = snprintf(path, sizeof(path), "%s%s", c->lxc_conf->shmount.path_cont, suff);
+		if (ret < 0 || (size_t)ret >= sizeof(path)) {
 			SYSERROR("Error writing container mountpoint name");
 			_exit(EXIT_FAILURE);
 		}