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11904167 KK |
1 | /* |
2 | * mmap based event notifications for SELinux | |
3 | * | |
4 | * Author: KaiGai Kohei <kaigai@ak.jp.nec.com> | |
5 | * | |
6 | * Copyright (C) 2010 NEC corporation | |
7 | * | |
8 | * This program is free software; you can redistribute it and/or modify | |
9 | * it under the terms of the GNU General Public License version 2, | |
10 | * as published by the Free Software Foundation. | |
11 | */ | |
12 | #include <linux/kernel.h> | |
13 | #include <linux/gfp.h> | |
14 | #include <linux/mm.h> | |
15 | #include <linux/mutex.h> | |
16 | #include "avc.h" | |
17 | #include "services.h" | |
18 | ||
19 | /* | |
20 | * The selinux_status_page shall be exposed to userspace applications | |
21 | * using mmap interface on /selinux/status. | |
22 | * It enables to notify applications a few events that will cause reset | |
23 | * of userspace access vector without context switching. | |
24 | * | |
25 | * The selinux_kernel_status structure on the head of status page is | |
26 | * protected from concurrent accesses using seqlock logic, so userspace | |
27 | * application should reference the status page according to the seqlock | |
28 | * logic. | |
29 | * | |
30 | * Typically, application checks status->sequence at the head of access | |
31 | * control routine. If it is odd-number, kernel is updating the status, | |
32 | * so please wait for a moment. If it is changed from the last sequence | |
33 | * number, it means something happen, so application will reset userspace | |
34 | * avc, if needed. | |
35 | * In most cases, application shall confirm the kernel status is not | |
36 | * changed without any system call invocations. | |
37 | */ | |
36f7f284 | 38 | static struct page *selinux_status_page; |
11904167 KK |
39 | static DEFINE_MUTEX(selinux_status_lock); |
40 | ||
41 | /* | |
42 | * selinux_kernel_status_page | |
43 | * | |
44 | * It returns a reference to selinux_status_page. If the status page is | |
45 | * not allocated yet, it also tries to allocate it at the first time. | |
46 | */ | |
47 | struct page *selinux_kernel_status_page(void) | |
48 | { | |
49 | struct selinux_kernel_status *status; | |
50 | struct page *result = NULL; | |
51 | ||
52 | mutex_lock(&selinux_status_lock); | |
36f7f284 | 53 | if (!selinux_status_page) { |
11904167 | 54 | selinux_status_page = alloc_page(GFP_KERNEL|__GFP_ZERO); |
36f7f284 KK |
55 | |
56 | if (selinux_status_page) { | |
11904167 KK |
57 | status = page_address(selinux_status_page); |
58 | ||
59 | status->version = SELINUX_KERNEL_STATUS_VERSION; | |
60 | status->sequence = 0; | |
61 | status->enforcing = selinux_enforcing; | |
949c2c1d | 62 | |
11904167 KK |
63 | /* |
64 | * NOTE: the next policyload event shall set | |
65 | * a positive value on the status->policyload, | |
66 | * although it may not be 1, but never zero. | |
67 | * So, application can know it was updated. | |
68 | */ | |
69 | status->policyload = 0; | |
70 | status->deny_unknown = !security_get_allow_unknown(); | |
71 | } | |
72 | } | |
73 | result = selinux_status_page; | |
74 | mutex_unlock(&selinux_status_lock); | |
75 | ||
76 | return result; | |
77 | } | |
78 | ||
79 | /* | |
80 | * selinux_status_update_setenforce | |
81 | * | |
82 | * It updates status of the current enforcing/permissive mode. | |
83 | */ | |
84 | void selinux_status_update_setenforce(int enforcing) | |
85 | { | |
86 | struct selinux_kernel_status *status; | |
87 | ||
88 | mutex_lock(&selinux_status_lock); | |
36f7f284 | 89 | if (selinux_status_page) { |
11904167 KK |
90 | status = page_address(selinux_status_page); |
91 | ||
92 | status->sequence++; | |
93 | smp_wmb(); | |
94 | ||
95 | status->enforcing = enforcing; | |
96 | ||
97 | smp_wmb(); | |
98 | status->sequence++; | |
99 | } | |
100 | mutex_unlock(&selinux_status_lock); | |
101 | } | |
102 | ||
103 | /* | |
104 | * selinux_status_update_policyload | |
105 | * | |
106 | * It updates status of the times of policy reloaded, and current | |
107 | * setting of deny_unknown. | |
108 | */ | |
109 | void selinux_status_update_policyload(int seqno) | |
110 | { | |
111 | struct selinux_kernel_status *status; | |
112 | ||
113 | mutex_lock(&selinux_status_lock); | |
36f7f284 | 114 | if (selinux_status_page) { |
11904167 KK |
115 | status = page_address(selinux_status_page); |
116 | ||
117 | status->sequence++; | |
118 | smp_wmb(); | |
119 | ||
120 | status->policyload = seqno; | |
121 | status->deny_unknown = !security_get_allow_unknown(); | |
122 | ||
123 | smp_wmb(); | |
124 | status->sequence++; | |
125 | } | |
126 | mutex_unlock(&selinux_status_lock); | |
127 | } |