Add `zfs allow` and `zfs unallow` support

ZFS allows for specific permissions to be delegated to normal users
with the `zfs allow` and `zfs unallow` commands.  In addition, non-
privileged users should be able to run all of the following commands:

  * zpool [list | iostat | status | get]
  * zfs [list | get]

Historically this functionality was not available on Linux.  In order
to add it the secpolicy_* functions needed to be implemented and mapped
to the equivalent Linux capability.  Only then could the permissions on
the `/dev/zfs` be relaxed and the internal ZFS permission checks used.

Even with this change some limitations remain.  Under Linux only the
root user is allowed to modify the namespace (unless it's a private
namespace).  This means the mount, mountpoint, canmount, unmount,
and remount delegations cannot be supported with the existing code.  It
may be possible to add this functionality in the future.

This functionality was validated with the cli_user and delegation test
cases from the ZFS Test Suite.  These tests exhaustively verify each
of the supported permissions which can be delegated and ensures only
an authorized user can perform it.

Two minor bug fixes were required for test-running.py.  First, the
Timer() object cannot be safely created in a `try:` block when there
is an unconditional `finally` block which references it.  Second,
when running as a normal user also check for scripts using the
both the .ksh and .sh suffixes.

Finally, existing users who are simulating delegations by setting
group permissions on the /dev/zfs device should revert that
customization when updating to a version with this change.

Signed-off-by: Brian Behlendorf <[email protected]>
Signed-off-by: Tony Hutter <[email protected]>
Closes #362 
Closes #434 
Closes #4100
Closes #4394 
Closes #4410 
Closes #4487 

1 files changed, 5 insertions, 3 deletions

diff --git a/man/man8/zfs.8 b/man/man8/zfs.8
index 30660a60d..4e3fa54a8 100644
--- a/man/man8/zfs.8
+++ b/man/man8/zfs.8
@@ -2933,6 +2933,11 @@ Force a rollback of the file system to the most recent snapshot before performin
 .sp .6
 .RS 4n
 Displays permissions that have been delegated on the specified filesystem or volume. See the other forms of \fBzfs allow\fR for more information.
+.sp
+Delegations are supported under Linux with the exception of \fBmount\fR,
+\fBunmount\fR, \fBmountpoint\fR, \fBcanmount\fR, \fBrename\fR, and \fBshare\fR.
+These permissions cannot be delegated because the Linux \fBmount(8)\fR command
+restricts modifications of the global namespace to the root user.
 .RE
 
 .sp
@@ -3584,9 +3589,6 @@ If you are using \fBDNS\fR for host name resolution, specify the fully qualified
 .LP
 \fBExample 17 \fRDelegating ZFS Administration Permissions on a ZFS Dataset
 .sp
-.LP
-This is not currently supported on Linux.
-.sp
 The following example shows how to set permissions so that user \fBcindys\fR can create, destroy, mount, and take snapshots on \fBtank/cindys\fR. The permissions on \fBtank/cindys\fR are also displayed.
 
 .sp