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/*
* mmap based event notifications for SELinux
*
* Author: KaiGai Kohei <kaigai@ak.jp.nec.com>
*
* Copyright (C) 2010 NEC corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2,
* as published by the Free Software Foundation.
*/
#include <linux/kernel.h>
#include <linux/gfp.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include "avc.h"
#include "services.h"
/*
* The selinux_status_page shall be exposed to userspace applications
* using mmap interface on /selinux/status.
* It enables to notify applications a few events that will cause reset
* of userspace access vector without context switching.
*
* The selinux_kernel_status structure on the head of status page is
* protected from concurrent accesses using seqlock logic, so userspace
* application should reference the status page according to the seqlock
* logic.
*
* Typically, application checks status->sequence at the head of access
* control routine. If it is odd-number, kernel is updating the status,
* so please wait for a moment. If it is changed from the last sequence
* number, it means something happen, so application will reset userspace
* avc, if needed.
* In most cases, application shall confirm the kernel status is not
* changed without any system call invocations.
*/
static struct page *selinux_status_page;
static DEFINE_MUTEX(selinux_status_lock);
/*
* selinux_kernel_status_page
*
* It returns a reference to selinux_status_page. If the status page is
* not allocated yet, it also tries to allocate it at the first time.
*/
struct page *selinux_kernel_status_page(void)
{
struct selinux_kernel_status *status;
struct page *result = NULL;
mutex_lock(&selinux_status_lock);
if (!selinux_status_page) {
selinux_status_page = alloc_page(GFP_KERNEL|__GFP_ZERO);
if (selinux_status_page) {
status = page_address(selinux_status_page);
status->version = SELINUX_KERNEL_STATUS_VERSION;
status->sequence = 0;
status->enforcing = selinux_enforcing;
/*
* NOTE: the next policyload event shall set
* a positive value on the status->policyload,
* although it may not be 1, but never zero.
* So, application can know it was updated.
*/
status->policyload = 0;
status->deny_unknown = !security_get_allow_unknown();
}
}
result = selinux_status_page;
mutex_unlock(&selinux_status_lock);
return result;
}
/*
* selinux_status_update_setenforce
*
* It updates status of the current enforcing/permissive mode.
*/
void selinux_status_update_setenforce(int enforcing)
{
struct selinux_kernel_status *status;
mutex_lock(&selinux_status_lock);
if (selinux_status_page) {
status = page_address(selinux_status_page);
status->sequence++;
smp_wmb();
status->enforcing = enforcing;
smp_wmb();
status->sequence++;
}
mutex_unlock(&selinux_status_lock);
}
/*
* selinux_status_update_policyload
*
* It updates status of the times of policy reloaded, and current
* setting of deny_unknown.
*/
void selinux_status_update_policyload(int seqno)
{
struct selinux_kernel_status *status;
mutex_lock(&selinux_status_lock);
if (selinux_status_page) {
status = page_address(selinux_status_page);
status->sequence++;
smp_wmb();
status->policyload = seqno;
status->deny_unknown = !security_get_allow_unknown();
smp_wmb();
status->sequence++;
}
mutex_unlock(&selinux_status_lock);
}
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