/* * mmap based event notifications for SELinux * * Author: KaiGai Kohei * * 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 #include #include #include #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); } a>

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