ZVOLs should not be allowed to have children

zfs create, receive and rename can bypass this hierarchy rule. Update
both userland and kernel module to prevent this issue and use pyzfs
unit tests to exercise the ioctls directly.

Note: this commit slightly changes zfs_ioc_create() ABI. This allow to
differentiate a generic error (EINVAL) from the specific case where we
tried to create a dataset below a ZVOL (ZFS_ERR_WRONG_PARENT).

Reviewed-by: Paul Dagnelie <[email protected]>
Reviewed-by: Matt Ahrens <[email protected]>
Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Tom Caputi <[email protected]>
Signed-off-by: loli10K <[email protected]>

1 files changed, 26 insertions, 0 deletions

diff --git a/module/zfs/dmu_objset.c b/module/zfs/dmu_objset.c
index a8304c18d..fa80e3a61 100644
--- a/module/zfs/dmu_objset.c
+++ b/module/zfs/dmu_objset.c
@@ -29,6 +29,7 @@
  * Copyright (c) 2016 Actifio, Inc. All rights reserved.
  * Copyright 2017 Nexenta Systems, Inc.
  * Copyright (c) 2017 Open-E, Inc. All Rights Reserved.
+ * Copyright (c) 2018, loli10K <[email protected]>. All rights reserved.
  */
 
 /* Portions Copyright 2010 Robert Milkowski */
@@ -1118,6 +1119,8 @@ dmu_objset_create_check(void *arg, dmu_tx_t *tx)
 	dmu_objset_create_arg_t *doca = arg;
 	dsl_pool_t *dp = dmu_tx_pool(tx);
 	dsl_dir_t *pdd;
+	dsl_dataset_t *parentds;
+	objset_t *parentos;
 	const char *tail;
 	int error;
 
@@ -1146,7 +1149,30 @@ dmu_objset_create_check(void *arg, dmu_tx_t *tx)
 
 	error = dsl_fs_ss_limit_check(pdd, 1, ZFS_PROP_FILESYSTEM_LIMIT, NULL,
 	    doca->doca_cred);
+	if (error != 0) {
+		dsl_dir_rele(pdd, FTAG);
+		return (error);
+	}
 
+	/* can't create below anything but filesystems (eg. no ZVOLs) */
+	error = dsl_dataset_hold_obj(pdd->dd_pool,
+	    dsl_dir_phys(pdd)->dd_head_dataset_obj, FTAG, &parentds);
+	if (error != 0) {
+		dsl_dir_rele(pdd, FTAG);
+		return (error);
+	}
+	error = dmu_objset_from_ds(parentds, &parentos);
+	if (error != 0) {
+		dsl_dataset_rele(parentds, FTAG);
+		dsl_dir_rele(pdd, FTAG);
+		return (error);
+	}
+	if (dmu_objset_type(parentos) != DMU_OST_ZFS) {
+		dsl_dataset_rele(parentds, FTAG);
+		dsl_dir_rele(pdd, FTAG);
+		return (SET_ERROR(ZFS_ERR_WRONG_PARENT));
+	}
+	dsl_dataset_rele(parentds, FTAG);
 	dsl_dir_rele(pdd, FTAG);
 
 	return (error);