MFV r302642:

6876 Stack corruption after importing a pool with a too-long name

illumos/illumos-gate@c971037baa
c971037baa

https://www.illumos.org/issues/6876
  Calling dsl_dataset_name on a dataset with a 256 byte buffer is asking for
  trouble. We should check every dataset on import, using a 1024 byte buffer and
  checking each time to see if the dataset's new name is longer than 256 bytes.

Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Yuri Pankov <yuri.pankov@nexenta.com>
Approved by: Richard Lowe <richlowe@richlowe.net>
Author: Paul Dagnelie <pcd@delphix.com>

cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c

@@ -1786,7 +1786,12 @@ zpool_import_props(libzfs_handle_t *hdl, nvlist_t *config, const char *newname,
 		case EEXIST:
 			(void) zpool_standard_error(hdl, error, desc);
 			break;
-
+		case ENAMETOOLONG:
+			zfs_error_aux(hdl, dgettext(TEXT_DOMAIN,
+			    "new name of at least one dataset is longer than "
+			    "the maximum allowable length"));
+			(void) zfs_error(hdl, EZFS_NAMETOOLONG, desc);
+			break;
 		default:
 			(void) zpool_standard_error(hdl, error, desc);
 			zpool_explain_recover(hdl,