1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * mmap based event notifications for SELinux 4 * 5 * Author: KaiGai Kohei <kaigai@ak.jp.nec.com> 6 * 7 * Copyright (C) 2010 NEC corporation 8 */ 9 #include <linux/kernel.h> 10 #include <linux/gfp.h> 11 #include <linux/mm.h> 12 #include <linux/mutex.h> 13 #include "avc.h" 14 #include "security.h" 15 16 /* 17 * The selinux_status_page shall be exposed to userspace applications 18 * using mmap interface on /selinux/status. 19 * It enables to notify applications a few events that will cause reset 20 * of userspace access vector without context switching. 21 * 22 * The selinux_kernel_status structure on the head of status page is 23 * protected from concurrent accesses using seqlock logic, so userspace 24 * application should reference the status page according to the seqlock 25 * logic. 26 * 27 * Typically, application checks status->sequence at the head of access 28 * control routine. If it is odd-number, kernel is updating the status, 29 * so please wait for a moment. If it is changed from the last sequence 30 * number, it means something happen, so application will reset userspace 31 * avc, if needed. 32 * In most cases, application shall confirm the kernel status is not 33 * changed without any system call invocations. 34 */ 35 36 /* 37 * selinux_kernel_status_page 38 * 39 * It returns a reference to selinux_status_page. If the status page is 40 * not allocated yet, it also tries to allocate it at the first time. 41 */ 42 struct page *selinux_kernel_status_page(void) 43 { 44 struct selinux_kernel_status *status; 45 struct page *result = NULL; 46 47 mutex_lock(&selinux_state.status_lock); 48 if (!selinux_state.status_page) { 49 selinux_state.status_page = alloc_page(GFP_KERNEL|__GFP_ZERO); 50 51 if (selinux_state.status_page) { 52 status = page_address(selinux_state.status_page); 53 54 status->version = SELINUX_KERNEL_STATUS_VERSION; 55 status->sequence = 0; 56 status->enforcing = enforcing_enabled(); 57 /* 58 * NOTE: the next policyload event shall set 59 * a positive value on the status->policyload, 60 * although it may not be 1, but never zero. 61 * So, application can know it was updated. 62 */ 63 status->policyload = 0; 64 status->deny_unknown = 65 !security_get_allow_unknown(); 66 } 67 } 68 result = selinux_state.status_page; 69 mutex_unlock(&selinux_state.status_lock); 70 71 return result; 72 } 73 74 /* 75 * selinux_status_update_setenforce 76 * 77 * It updates status of the current enforcing/permissive mode. 78 */ 79 void selinux_status_update_setenforce(int enforcing) 80 { 81 struct selinux_kernel_status *status; 82 83 mutex_lock(&selinux_state.status_lock); 84 if (selinux_state.status_page) { 85 status = page_address(selinux_state.status_page); 86 87 status->sequence++; 88 smp_wmb(); 89 90 status->enforcing = enforcing; 91 92 smp_wmb(); 93 status->sequence++; 94 } 95 mutex_unlock(&selinux_state.status_lock); 96 } 97 98 /* 99 * selinux_status_update_policyload 100 * 101 * It updates status of the times of policy reloaded, and current 102 * setting of deny_unknown. 103 */ 104 void selinux_status_update_policyload(int seqno) 105 { 106 struct selinux_kernel_status *status; 107 108 mutex_lock(&selinux_state.status_lock); 109 if (selinux_state.status_page) { 110 status = page_address(selinux_state.status_page); 111 112 status->sequence++; 113 smp_wmb(); 114 115 status->policyload = seqno; 116 status->deny_unknown = !security_get_allow_unknown(); 117 118 smp_wmb(); 119 status->sequence++; 120 } 121 mutex_unlock(&selinux_state.status_lock); 122 } 123