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]>

3 files changed, 96 insertions, 1 deletions

diff --git a/tests/runfiles/linux.run b/tests/runfiles/linux.run
index d3ecf6274..8ab5e7033 100644
--- a/tests/runfiles/linux.run
+++ b/tests/runfiles/linux.run
@@ -887,7 +887,8 @@ tags = ['functional', 'zvol', 'zvol_cli']
 [tests/functional/zvol/zvol_misc]
 tests = ['zvol_misc_001_neg', 'zvol_misc_002_pos', 'zvol_misc_003_neg',
     'zvol_misc_004_pos', 'zvol_misc_005_neg', 'zvol_misc_006_pos',
-    'zvol_misc_snapdev', 'zvol_misc_volmode', 'zvol_misc_zil']
+    'zvol_misc_hierarchy', 'zvol_misc_snapdev', 'zvol_misc_volmode',
+    'zvol_misc_zil']
 tags = ['functional', 'zvol', 'zvol_misc']
 
 [tests/functional/zvol/zvol_swap]
diff --git a/tests/zfs-tests/tests/functional/zvol/zvol_misc/Makefile.am b/tests/zfs-tests/tests/functional/zvol/zvol_misc/Makefile.am
index a2c95a3eb..57ffbd565 100644
--- a/tests/zfs-tests/tests/functional/zvol/zvol_misc/Makefile.am
+++ b/tests/zfs-tests/tests/functional/zvol/zvol_misc/Makefile.am
@@ -8,6 +8,7 @@ dist_pkgdata_SCRIPTS = \
 	zvol_misc_004_pos.ksh \
 	zvol_misc_005_neg.ksh \
 	zvol_misc_006_pos.ksh \
+	zvol_misc_hierarchy.ksh \
 	zvol_misc_snapdev.ksh \
 	zvol_misc_volmode.ksh \
 	zvol_misc_zil.ksh
diff --git a/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_hierarchy.ksh b/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_hierarchy.ksh
new file mode 100755
index 000000000..1431f0b1f
--- /dev/null
+++ b/tests/zfs-tests/tests/functional/zvol/zvol_misc/zvol_misc_hierarchy.ksh
@@ -0,0 +1,93 @@
+#!/bin/ksh -p
+#
+# CDDL HEADER START
+#
+# This file and its contents are supplied under the terms of the
+# Common Development and Distribution License ("CDDL"), version 1.0.
+# You may only use this file in accordance with the terms of version
+# 1.0 of the CDDL.
+#
+# A full copy of the text of the CDDL should have accompanied this
+# source.  A copy of the CDDL is also available via the Internet at
+# http://www.illumos.org/license/CDDL.
+#
+# CDDL HEADER END
+#
+
+#
+# Copyright 2018, loli10K <[email protected]>. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+
+#
+# DESCRIPTION:
+# ZVOLs cannot have children datasets: verify zfs commands respect this
+# hierarchy rule.
+#
+# STRATEGY:
+# 1. Create a filesystem and a ZVOL
+# 2. Verify 'zfs recv' will not (force-)receive a ZVOL over the root dataset
+# 3. Verify 'zfs recv' cannot receive a ZVOL overwriting datasets with children
+# 4. Verify 'zfs recv' cannot receive datasets below a ZVOL
+# 5. Verify 'zfs create' cannot create datasets under a ZVOL
+# 6. Verify 'zfs rename' cannot move datasets under a ZVOL
+#
+
+verify_runnable "both"
+
+function cleanup
+{
+	destroy_pool "$poolname"
+	log_must rm -f "$vdevfile" "$streamfile_fs" "$streamfile_zvol"
+}
+
+log_assert "ZVOLs cannot have children datasets: verify zfs commands respect "\
+	"this hierarchy rule"
+log_onexit cleanup
+
+poolname="$TESTPOOL-zvol_hierarchy"
+vdevfile="$TEST_BASE_DIR/vdevfile.$$"
+streamfile_fs="$TEST_BASE_DIR/streamfile_fs.$$"
+streamfile_zvol="$TEST_BASE_DIR/streamfile_zvol.$$"
+
+# 1. Create filesystems and ZVOLs
+# NOTE: set "mountpoint=none" just to speed up the test process
+log_must truncate -s $MINVDEVSIZE "$vdevfile"
+log_must zpool create -O mountpoint=none "$poolname" "$vdevfile"
+log_must zfs create "$poolname/sendfs"
+log_must zfs create -V 1M -s "$poolname/sendvol"
+log_must zfs snapshot "$poolname/sendfs@snap"
+log_must zfs snapshot "$poolname/sendvol@snap"
+log_must eval "zfs send $poolname/sendfs@snap > $streamfile_fs"
+log_must eval "zfs send $poolname/sendvol@snap > $streamfile_zvol"
+
+# 2. Verify 'zfs recv' will not (force-)receive a ZVOL over the root dataset
+log_mustnot eval "zfs receive -F $poolname < $streamfile_zvol"
+
+# 3. Verify 'zfs recv' cannot receive a ZVOL overwriting datasets with children
+log_must zfs create "$poolname/fs"
+log_must zfs create "$poolname/fs/subfs"
+log_mustnot eval "zfs receive -F $poolname/fs < $streamfile_zvol"
+log_must zfs destroy "$poolname/fs/subfs"
+log_must eval "zfs receive -F $poolname/fs < $streamfile_zvol"
+
+# 4. Verify 'zfs recv' cannot receive datasets below a ZVOL
+log_must zfs create -V 1M -s "$poolname/volume"
+log_mustnot eval "zfs receive $poolname/volume/subfs < $streamfile_fs"
+log_mustnot eval "zfs receive $poolname/volume/subvol < $streamfile_zvol"
+
+# 5. Verify 'zfs create' cannot create datasets under a ZVOL
+log_must zfs create -V 1M -s "$poolname/createvol"
+log_mustnot zfs create "$poolname/createvol/fs"
+log_mustnot zfs create -V 1M -s "$poolname/createvol/vol"
+
+# 6. Verify 'zfs rename' cannot move datasets under a ZVOL
+log_must zfs create "$poolname/movefs"
+log_must zfs create -V 1M -s "$poolname/movevol"
+log_must zfs create -V 1M -s "$poolname/renamevol"
+log_mustnot zfs rename "$poolname/fs" "$poolname/renamevol/fs"
+log_mustnot zfs rename "$poolname/vol" "$poolname/renamevol/vol"
+
+log_pass "ZVOLs cannot have children datasets and zfs commands enforce this "\
+	"rule"