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(lock: &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(bool 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 ? 1 : 0; |
91 | |
92 | smp_wmb(); |
93 | status->sequence++; |
94 | } |
95 | mutex_unlock(lock: &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(u32 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(lock: &selinux_state.status_lock); |
122 | } |
123 | |