HardenedBSD/sys/security/mac_priority/mac_priority.c
Florian Walpen e28767f0e1 Thread creation privilege for realtime group
With the mac_priority(4) realtime policy active, users and processes in
the realtime group may promote existing threads and processes to
realtime scheduling priority. Extend the privileges granted to
PRIV_SCHED_SETPOLICY which allows explicit creation of new realtime
threads.

One use case of this is when the pthread scheduling policy is set to
SCHED_RR or SCHED_FIFO via pthread_attr_setschedpolicy(...) before
calling pthread_create(...). I ran into this when testing audio software
with realtime threads, particularly audio/ardour6.

MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D33393
2021-12-15 00:01:58 +02:00

84 lines
3.0 KiB
C

/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2021 Florian Walpen <dev@submerge.ch>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/param.h>
#include <sys/conf.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/priv.h>
#include <sys/sysctl.h>
#include <sys/ucred.h>
#include <security/mac/mac_policy.h>
SYSCTL_DECL(_security_mac);
static SYSCTL_NODE(_security_mac, OID_AUTO, priority,
CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
"mac_priority policy controls");
static int realtime_enabled = 1;
SYSCTL_INT(_security_mac_priority, OID_AUTO, realtime, CTLFLAG_RWTUN,
&realtime_enabled, 0,
"Enable realtime priority scheduling for group realtime_gid");
static int realtime_gid = GID_RT_PRIO;
SYSCTL_INT(_security_mac_priority, OID_AUTO, realtime_gid, CTLFLAG_RWTUN,
&realtime_gid, 0,
"Group id of the realtime privilege group");
static int idletime_enabled = 1;
SYSCTL_INT(_security_mac_priority, OID_AUTO, idletime, CTLFLAG_RWTUN,
&idletime_enabled, 0,
"Enable idle priority scheduling for group idletime_gid");
static int idletime_gid = GID_ID_PRIO;
SYSCTL_INT(_security_mac_priority, OID_AUTO, idletime_gid, CTLFLAG_RWTUN,
&idletime_gid, 0,
"Group id of the idletime privilege group");
static int
priority_priv_grant(struct ucred *cred, int priv)
{
if ((priv == PRIV_SCHED_RTPRIO || priv == PRIV_SCHED_SETPOLICY) &&
realtime_enabled && groupmember(realtime_gid, cred))
return (0);
if (priv == PRIV_SCHED_IDPRIO && idletime_enabled &&
groupmember(idletime_gid, cred))
return (0);
return (EPERM);
}
static struct mac_policy_ops priority_ops = {
.mpo_priv_grant = priority_priv_grant,
};
MAC_POLICY_SET(&priority_ops, mac_priority, "MAC/priority",
MPC_LOADTIME_FLAG_UNLOADOK, NULL);