Device removal of indirect vdev panics the kernel

This commit fixes a NULL pointer dereference triggered in
spa_vdev_remove_top_check() by trying to "zpool remove" an indirect
vdev.

Reviewed-by: Matt Ahrens <matt@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes openzfs#9327

module/zfs/vdev_removal.c

@@ -22,6 +22,7 @@
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
  * Copyright (c) 2011, 2019 by Delphix. All rights reserved.
+ * Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
  */
 
 #include <sys/zfs_context.h>
@@ -1936,6 +1937,9 @@ spa_vdev_remove_top_check(vdev_t *vd)
 	if (vd != vd->vdev_top)
 		return (SET_ERROR(ENOTSUP));
 
+	if (!vdev_is_concrete(vd))
+		return (SET_ERROR(ENOTSUP));
+
 	if (!spa_feature_is_enabled(spa, SPA_FEATURE_DEVICE_REMOVAL))
 		return (SET_ERROR(ENOTSUP));
 

tests/runfiles/linux.run

@@ -772,7 +772,8 @@ tests = ['removal_all_vdev', 'removal_cancel', 'removal_check_space',
     'removal_with_remove', 'removal_with_scrub', 'removal_with_send',
     'removal_with_send_recv', 'removal_with_snapshot',
     'removal_with_write', 'removal_with_zdb', 'remove_expanded',
-    'remove_mirror', 'remove_mirror_sanity', 'remove_raidz']
+    'remove_mirror', 'remove_mirror_sanity', 'remove_raidz',
+    'remove_indirect']
 tags = ['functional', 'removal']
 
 [tests/functional/rename_dirs]

tests/zfs-tests/tests/functional/removal/Makefile.am

@@ -29,7 +29,7 @@ dist_pkgdata_SCRIPTS = \
 	removal_with_send.ksh removal_with_send_recv.ksh \
 	removal_with_snapshot.ksh removal_with_write.ksh \
 	removal_with_zdb.ksh remove_mirror.ksh remove_mirror_sanity.ksh \
-	remove_raidz.ksh remove_expanded.ksh
+	remove_raidz.ksh remove_expanded.ksh remove_indirect.ksh
 
 dist_pkgdata_DATA = \
 	removal.kshlib

tests/zfs-tests/tests/functional/removal/remove_indirect.ksh

@@ -0,0 +1,58 @@
+#!/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 2019, loli10K <ezomori.nozomu@gmail.com>. All rights reserved.
+#
+
+. $STF_SUITE/include/libtest.shlib
+. $STF_SUITE/tests/functional/removal/removal.kshlib
+
+#
+# DESCRIPTION:
+# Device removal cannot remove non-concrete vdevs
+#
+# STRATEGY:
+# 1. Create a pool with removable devices
+# 2. Remove a top-level device
+# 3. Verify we can't remove the "indirect" vdev created by the first removal
+#
+
+verify_runnable "global"
+
+function cleanup
+{
+	destroy_pool $TESTPOOL
+	log_must rm -f $TEST_BASE_DIR/device-{1,2,3}
+}
+
+log_assert "Device removal should not be able to remove non-concrete vdevs"
+log_onexit cleanup
+
+# 1. Create a pool with removable devices
+truncate -s $MINVDEVSIZE $TEST_BASE_DIR/device-{1,2,3}
+zpool create $TESTPOOL $TEST_BASE_DIR/device-{1,2,3}
+
+# 2. Remove a top-level device
+log_must zpool remove $TESTPOOL $TEST_BASE_DIR/device-1
+log_must wait_for_removal $TESTPOOL
+
+# 3. Verify we can't remove the "indirect" vdev created by the first removal
+INDIRECT_VDEV=$(zpool list -v -g $TESTPOOL | awk '{if ($2 == "-") { print $1; exit} }')
+log_must test -n "$INDIRECT_VDEV"
+log_mustnot zpool remove $TESTPOOL $INDIRECT_VDEV
+
+log_pass "Device removal cannot remove non-concrete vdevs"