2 * mmap based event notifications for SELinux
4 * Author: KaiGai Kohei <kaigai@ak.jp.nec.com>
6 * Copyright (C) 2010 NEC corporation
8 * This program is free software; you can redistribute it and/or modify
9 * it under the terms of the GNU General Public License version 2,
10 * as published by the Free Software Foundation.
12 #include <linux/kernel.h>
13 #include <linux/gfp.h>
15 #include <linux/mutex.h>
20 * The selinux_status_page shall be exposed to userspace applications
21 * using mmap interface on /selinux/status.
22 * It enables to notify applications a few events that will cause reset
23 * of userspace access vector without context switching.
25 * The selinux_kernel_status structure on the head of status page is
26 * protected from concurrent accesses using seqlock logic, so userspace
27 * application should reference the status page according to the seqlock
30 * Typically, application checks status->sequence at the head of access
31 * control routine. If it is odd-number, kernel is updating the status,
32 * so please wait for a moment. If it is changed from the last sequence
33 * number, it means something happen, so application will reset userspace
35 * In most cases, application shall confirm the kernel status is not
36 * changed without any system call invocations.
38 static struct page *selinux_status_page = NULL;
39 static DEFINE_MUTEX(selinux_status_lock);
42 * selinux_kernel_status_page
44 * It returns a reference to selinux_status_page. If the status page is
45 * not allocated yet, it also tries to allocate it at the first time.
47 struct page *selinux_kernel_status_page(void)
49 struct selinux_kernel_status *status;
50 struct page *result = NULL;
52 mutex_lock(&selinux_status_lock);
53 if (!selinux_status_page)
55 selinux_status_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
56 if (selinux_status_page)
58 status = page_address(selinux_status_page);
60 status->version = SELINUX_KERNEL_STATUS_VERSION;
62 status->enforcing = selinux_enforcing;
64 * NOTE: the next policyload event shall set
65 * a positive value on the status->policyload,
66 * although it may not be 1, but never zero.
67 * So, application can know it was updated.
69 status->policyload = 0;
70 status->deny_unknown = !security_get_allow_unknown();
73 result = selinux_status_page;
74 mutex_unlock(&selinux_status_lock);
80 * selinux_status_update_setenforce
82 * It updates status of the current enforcing/permissive mode.
84 void selinux_status_update_setenforce(int enforcing)
86 struct selinux_kernel_status *status;
88 mutex_lock(&selinux_status_lock);
89 if (selinux_status_page)
91 status = page_address(selinux_status_page);
96 status->enforcing = enforcing;
101 mutex_unlock(&selinux_status_lock);
105 * selinux_status_update_policyload
107 * It updates status of the times of policy reloaded, and current
108 * setting of deny_unknown.
110 void selinux_status_update_policyload(int seqno)
112 struct selinux_kernel_status *status;
114 mutex_lock(&selinux_status_lock);
115 if (selinux_status_page)
117 status = page_address(selinux_status_page);
122 status->policyload = seqno;
123 status->deny_unknown = !security_get_allow_unknown();
128 mutex_unlock(&selinux_status_lock);