kern_pax.c revision 1.3 
1/* $NetBSD: kern_pax.c,v 1.3 2006/05/20 15:45:37 elad Exp $ */
2
3/*-
4 * Copyright (c) 2006 Elad Efrat <elad@NetBSD.org>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions
9 * are met:
10 * 1. Redistributions of source code must retain the above copyright
11 *    notice, this list of conditions and the following disclaimer.
12 * 2. Redistributions in binary form must reproduce the above copyright
13 *    notice, this list of conditions and the following disclaimer in the
14 *    documentation and/or other materials provided with the distribution.
15 * 3. All advertising materials mentioning features or use of this software
16 *    must display the following acknowledgement:
17 *      This product includes software developed by Elad Efrat.
18 * 4. The name of the author may not be used to endorse or promote products
19 *    derived from this software without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33#include "opt_pax.h"
34
35#include <sys/param.h>
36#include <sys/proc.h>
37#include <sys/exec_elf.h>
38#include <uvm/uvm_extern.h>
39#include <sys/pax.h>
40#include <sys/sysctl.h>
41
42int pax_mprotect_enabled = 1;
43int pax_mprotect_global = PAX_MPROTECT;
44
45SYSCTL_SETUP(sysctl_security_pax_setup, "sysctl security.pax setup")
46{
47	const struct sysctlnode *rnode = NULL;
48
49        sysctl_createv(clog, 0, NULL, &rnode,
50                       CTLFLAG_PERMANENT,
51                       CTLTYPE_NODE, "security", NULL,
52                       NULL, 0, NULL, 0,
53                       CTL_CREATE, CTL_EOL);
54
55	sysctl_createv(clog, 0, &rnode, &rnode,
56		       CTLFLAG_PERMANENT,
57		       CTLTYPE_NODE, "pax",
58		       SYSCTL_DESCR("PaX (exploit mitigation) features."),
59		       NULL, 0, NULL, 0,
60		       CTL_CREATE, CTL_EOL);
61
62	sysctl_createv(clog, 0, &rnode, &rnode,
63		       CTLFLAG_PERMANENT,
64		       CTLTYPE_NODE, "mprotect",
65		       SYSCTL_DESCR("mprotect(2) W^X restrictions."),
66		       NULL, 0, NULL, 0,
67		       CTL_CREATE, CTL_EOL);
68	sysctl_createv(clog, 0, &rnode, NULL,
69		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
70		       CTLTYPE_INT, "enabled",
71		       SYSCTL_DESCR("Restrictions enabled."),
72		       NULL, 0, &pax_mprotect_enabled, 0,
73		       CTL_CREATE, CTL_EOL);
74	sysctl_createv(clog, 0, &rnode, NULL,
75		       CTLFLAG_PERMANENT|CTLFLAG_READWRITE,
76		       CTLTYPE_INT, "global_protection",
77		       SYSCTL_DESCR("When enabled, unless explicitly "
78				    "specified, apply restrictions to"
79				    "all processes."),
80		       NULL, 0, &pax_mprotect_global, 0,
81		       CTL_CREATE, CTL_EOL);
82}
83
84void
85pax_mprotect_adjust(struct lwp *l, int f)
86{
87	if (!pax_mprotect_enabled)
88		return;
89
90	if (f & PF_PAXMPROTECT)
91		l->l_proc->p_flag |= P_PAXMPROTECT;
92	if (f & PF_PAXNOMPROTECT)
93		l->l_proc->p_flag |= P_PAXNOMPROTECT;
94}
95
96void
97pax_mprotect(struct lwp *l, vm_prot_t *prot, vm_prot_t *maxprot)
98{
99	if (!pax_mprotect_enabled ||
100	    (pax_mprotect_global && (l->l_proc->p_flag & P_PAXNOMPROTECT)) ||
101	    (!pax_mprotect_global && !(l->l_proc->p_flag & P_PAXMPROTECT)))
102		return;
103
104	if ((*prot & (VM_PROT_WRITE|VM_PROT_EXECUTE)) != VM_PROT_EXECUTE) {
105		*prot &= ~VM_PROT_EXECUTE;
106		*maxprot &= ~VM_PROT_EXECUTE;
107	} else {
108		*prot &= ~VM_PROT_WRITE;
109		*maxprot &= ~VM_PROT_WRITE;
110	}
111}
112