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