conf: fix ephemeral copies

Don't rely on rootfs->bdev_type because that may be NULL. Use storage->type
instead which can't be NULL.

Co-Developed-by: Mathias Gibbens <[email protected]>
Signed-off-by: Mathias Gibbens <[email protected]>
Reported-by: Mathias Gibbens <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

src/lxc/conf.c

@@ -536,16 +536,21 @@ int lxc_rootfs_init(struct lxc_conf *conf, bool userns)
 	struct stat st;
 	struct statfs stfs;
 	struct lxc_rootfs *rootfs = &conf->rootfs;
+	const char *type;
 
 	ret = lxc_storage_prepare(conf);
 	if (ret)
 		return syserror_set(-EINVAL, "Failed to prepare rootfs storage");
+	type = rootfs->storage->type;
+
+	if (!type)
+		return syserror_set(-EINVAL, "Storage type neither set nor automatically detected");
 
 	if (!is_empty_string(rootfs->mnt_opts.userns_path)) {
 		if (!rootfs->path)
 			return syserror_set(-EINVAL, "Idmapped rootfs currently only supported with separate rootfs for container");
 
-		if (rootfs->bdev_type && !strequal(rootfs->bdev_type, "dir"))
+		if (type && !strequal(type, "dir"))
 			return syserror_set(-EINVAL, "Idmapped rootfs currently only supports the \"dir\" storage driver");
 	}
 
@@ -555,14 +560,12 @@ int lxc_rootfs_init(struct lxc_conf *conf, bool userns)
 	if (userns)
 		return log_trace(0, "Not pinning because container runs in user namespace");
 
-	if (rootfs->bdev_type) {
-		if (strequal(rootfs->bdev_type, "overlay") ||
-		    strequal(rootfs->bdev_type, "overlayfs"))
-			return log_trace_errno(0, EINVAL, "Not pinning on stacking filesystem");
+	if (strequal(type, "overlay") ||
+	    strequal(type, "overlayfs"))
+		return log_trace_errno(0, EINVAL, "Not pinning on stacking filesystem");
 
-		if (strequal(rootfs->bdev_type, "zfs"))
-			return log_trace_errno(0, EINVAL, "Not pinning on ZFS filesystem");
-	}
+	if (strequal(type, "zfs"))
+		return log_trace_errno(0, EINVAL, "Not pinning on ZFS filesystem");
 
 	dfd_path = open_at(-EBADF, rootfs->path, PROTECT_OPATH_FILE, 0, 0);
 	if (dfd_path < 0)
@@ -4831,8 +4834,8 @@ void lxc_conf_free(struct lxc_conf *conf)
 	if (current_config == conf)
 		current_config = NULL;
 	lxc_terminal_conf_free(&conf->console);
+	free(conf->rootfs.__bdev_type);
 	free(conf->rootfs.mount);
-	free(conf->rootfs.bdev_type);
 	free(conf->rootfs.path);
 	put_lxc_rootfs(&conf->rootfs, true);
 	free(conf->logfile);

src/lxc/conf.h

@@ -233,7 +233,7 @@ struct lxc_mount_options {
  * @path         : the rootfs source (directory or device)
  * @mount        : where it is mounted
  * @buf		 : static buffer to construct paths
- * @bdev_type     : optional backing store type
+ * @__bdev_type    : optional backing store type
  * @managed      : whether it is managed by LXC
  * @dfd_mnt	 : fd for @mount
  * @dfd_dev : fd for /dev of the container
@@ -251,7 +251,7 @@ struct lxc_rootfs {
 	int dfd_dev;
 
 	char buf[PATH_MAX];
-	char *bdev_type;
+	char *__bdev_type;
 	bool managed;
 	struct lxc_mount_options mnt_opts;
 	struct lxc_storage *storage;

src/lxc/confile.c

@@ -2795,14 +2795,14 @@ static int set_config_rootfs_path(const char *key, const char *value,
 		return ret_errno(ENOMEM);
 
 	/* Split <storage type>:<container path> into <storage type> and
-	 * <container path>. Set "rootfs.bdev_type" to <storage type> and
+	 * <container path>. Set "rootfs.__bdev_type" to <storage type> and
 	 * "rootfs.path" to <container path>.
 	 */
 	tmp = strchr(dup, ':');
 	if (tmp) {
 		*tmp = '\0';
 
-		ret = set_config_path_item(&lxc_conf->rootfs.bdev_type, dup);
+		ret = set_config_path_item(&lxc_conf->rootfs.__bdev_type, dup);
 		if (ret < 0)
 			return ret_errno(ENOMEM);
 

src/lxc/storage/storage.c

@@ -215,7 +215,7 @@ static const struct lxc_storage_type *storage_query(struct lxc_conf *conf)
 	size_t i;
 	const struct lxc_storage_type *bdev;
 	const char *path = conf->rootfs.path;
-	const char *type = conf->rootfs.bdev_type;
+	const char *type = conf->rootfs.__bdev_type;
 
 	bdev = get_storage_by_name(path, type);
 	if (bdev)
@@ -641,7 +641,7 @@ struct lxc_storage *storage_init(struct lxc_conf *conf)
 bool storage_lxc_is_dir(struct lxc_conf *conf)
 {
 	struct lxc_storage *orig;
-	char *type = conf->rootfs.bdev_type;
+	const char *type = conf->rootfs.__bdev_type;
 	bool bret = false;
 
 	if (type)

src/lxc/storage/storage.h

@@ -98,7 +98,7 @@ struct lxc_storage {
  *                  trust the config file. If the config file key
  *                  lxc.rootfs.path is set to <storage type>:<container path>
  *                  the confile parser will have split this into <storage type>
- *                  and <container path> and set the <bdev_type> member in the
+ *                  and <container path> and set the <__bdev_type> member in the
  *                  lxc_rootfs struct to <storage type> and the <path> member
  *                  will be set to a clean <container path> without the <storage
  *                  type> prefix. This is the new, clean way of handling storage