7019 zfsdev_ioctl skips secpolicy when FKIOCTL is set

7020 sdev_cleandir can loop forever

Note that the bulk of the upstream change is not applicable to FreeBSD
and the affected files are not even in the vendor area.

illumos/illumos-gate@45b1747515
45b1747515

https://www.illumos.org/issues/7019
  Currently zfsdev_ioctl, when confronted by a request with the FKIOCTL flag set,
  skips all processing of secpolicy functions. This means that ZFS is not doing
  any kind of verification of the credentials or access rights of the caller and
  assuming that (as it is an in-kernel client) all such checks have already been
  done.
  This turns out to be quite a dangerous assumption, especially with respect to
  sdev. In general I don't think it's particularly reasonable to offload this
  enforcement of access rights onto other kernel subsystems when ZFS has some
  particular local semantics in this area (delegated datasets etc) and does not
  provide any kind of API to allow other subsystems to avoid code duplication
  when doing it. ZFS should apply its normal access policy to requests from
  within the kernel, and callers should take care to give it the correct
  credentials and call it from the correct context in order to get the results
  they need.
  You can observe the currently unfortunate consequences of this bug in any non-
  global zone that has access to /dev/zvol or any subset of it via sdev profiles.
  In particular, a zone used to contain a KVM or similar which has a single zvol
  passed through to it using a <device match= block in its zone XML.
  Even though sdev makes something of an attempt to control for whether the
  caller should have access to nodes in /dev/zvol, it doesn't do this correctly,
  or really at all in the lookup call path. So, if we have a zone that's been
  given access to any part of /dev/zvol, it can simply look up the full path to
  any other zvol on the entire system, and the node will appear and be able to be
  used.

https://www.illumos.org/issues/7020
  sdev_cleandir can currently hang forever when it encounters a child node that
  is busy, or when it is given a matching expr and the first entry on the list
  does not match.
  The previous code (circa 2013) iterated over the children of the node using a
  for loop with SDEV_NEXT_ENTRY, which was then changed to a while ((dv =
  SDEV_FIRST_ENTRY(ddv)) { loop. Unfortunately the continue statements that
  previously made it skip over an entry were left as they were, which now result
  in an infinite busy-loop in the kernel.
  You can trigger this pretty easily by setting up an sdev exclude rule in
  zonecfg.
  Diagnosis: look for a runaway process consuming 100% CPU in kernel -- they have
  a distinctive stack:
  # mdb -k
  > 0t1234::pid2proc | ::walk thread | ::findstack -v
  [ ffffd001efcd3310 _resume_from_idle+0x112() ]
    ffffd001efcd3360 apix_hilevel_intr_epilog+0xc1(ffffd001efcd33d0, 0)
    ffffd001efcd33c0 apix_do_interrupt+0x34a(ffffd001efcd33d0, 0)
    ffffd001efcd33d0 _sys_rtt_ints_disabled+8()
    ffffd001efcd3550 rw_enter+0x58()
    ffffd001efcd35e0 sdev_cleandir+0x60(ffffd0631b6d75d8, 0, 0)
    ffffd001efcd3630 devzvol_prunedir+0xec(ffffd0631b6d76e8)
    ffffd001efcd36d0 devzvol_readdir+0x150(ffffd06333250e00, ffffd001efcd3790,
  ffffd062dc990e18, ffffd001efcd37dc, 0, 0)
    ffffd001efcd3760 fop_readdir+0x6b(ffffd06333250e00, ffffd001efcd3790,
  ffffd062dc990e18, ffffd001efcd37dc, 0, 0)
    ffffd001efcd3830 walk_dir+0xee(ffffd06333250e00, ffffd0669e4483c8,
  fffffffffbbdf410)
    ffffd001efcd3850 prof_make_names_walk+0x2e(ffffd0669e4483c8,
  fffffffffbbdf410)
    ffffd001efcd38b0 prof_make_names+0xfc(ffffd0669e4483c8)

Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Alex Wilson <alex.wilson@joyent.com>

uts/common/fs/zfs/zfs_ioctl.c

@@ -25,7 +25,7 @@
  * Portions Copyright 2011 Martin Matuska
  * Copyright 2015, OmniTI Computer Consulting, Inc. All rights reserved.
  * Copyright 2015 Nexenta Systems, Inc.  All rights reserved.
- * Copyright (c) 2014, Joyent, Inc. All rights reserved.
+ * Copyright (c) 2014, 2016 Joyent, Inc. All rights reserved.
  * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
@@ -6022,7 +6022,7 @@ zfsdev_ioctl(dev_t dev, int cmd, intptr_t arg, int flag, cred_t *cr, int *rvalp)
 	}
 
 
-	if (error == 0 && !(flag & FKIOCTL))
+	if (error == 0)
 		error = vec->zvec_secpolicy(zc, innvl, cr);
 
 	if (error != 0)