1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3 * AppArmor security module
4 *
5 * This file contains AppArmor contexts used to associate "labels" to objects.
6 *
7 * Copyright (C) 1998-2008 Novell/SUSE
8 * Copyright 2009-2010 Canonical Ltd.
9 */
10
11 #ifndef __AA_CONTEXT_H
12 #define __AA_CONTEXT_H
13
14 #include <linux/cred.h>
15 #include <linux/slab.h>
16 #include <linux/sched.h>
17
18 #include "label.h"
19 #include "policy_ns.h"
20 #include "task.h"
21
cred_label(const struct cred * cred)22 static inline struct aa_label *cred_label(const struct cred *cred)
23 {
24 struct aa_label **blob = cred->security + apparmor_blob_sizes.lbs_cred;
25
26 AA_BUG(!blob);
27 return *blob;
28 }
29
set_cred_label(const struct cred * cred,struct aa_label * label)30 static inline void set_cred_label(const struct cred *cred,
31 struct aa_label *label)
32 {
33 struct aa_label **blob = cred->security + apparmor_blob_sizes.lbs_cred;
34
35 AA_BUG(!blob);
36 *blob = label;
37 }
38
39 /**
40 * aa_get_newest_cred_label - obtain the newest label on a cred
41 * @cred: cred to obtain label from (NOT NULL)
42 *
43 * Returns: newest version of confining label
44 */
aa_get_newest_cred_label(const struct cred * cred)45 static inline struct aa_label *aa_get_newest_cred_label(const struct cred *cred)
46 {
47 return aa_get_newest_label(cred_label(cred));
48 }
49
aa_get_newest_cred_label_condref(const struct cred * cred,bool * needput)50 static inline struct aa_label *aa_get_newest_cred_label_condref(const struct cred *cred,
51 bool *needput)
52 {
53 struct aa_label *l = cred_label(cred);
54
55 if (unlikely(label_is_stale(l))) {
56 *needput = true;
57 return aa_get_newest_label(l);
58 }
59
60 *needput = false;
61 return l;
62 }
63
aa_put_label_condref(struct aa_label * l,bool needput)64 static inline void aa_put_label_condref(struct aa_label *l, bool needput)
65 {
66 if (unlikely(needput))
67 aa_put_label(l);
68 }
69
70 /**
71 * aa_current_raw_label - find the current tasks confining label
72 *
73 * Returns: up to date confining label or the ns unconfined label (NOT NULL)
74 *
75 * This fn will not update the tasks cred to the most up to date version
76 * of the label so it is safe to call when inside of locks.
77 */
aa_current_raw_label(void)78 static inline struct aa_label *aa_current_raw_label(void)
79 {
80 return cred_label(current_cred());
81 }
82
83 /**
84 * aa_get_current_label - get the newest version of the current tasks label
85 *
86 * Returns: newest version of confining label (NOT NULL)
87 *
88 * This fn will not update the tasks cred, so it is safe inside of locks
89 *
90 * The returned reference must be put with aa_put_label()
91 */
aa_get_current_label(void)92 static inline struct aa_label *aa_get_current_label(void)
93 {
94 struct aa_label *l = aa_current_raw_label();
95
96 if (label_is_stale(l))
97 return aa_get_newest_label(l);
98 return aa_get_label(l);
99 }
100
101 /**
102 * __end_cred_crit_section - end crit section begun with __begin_...
103 * @label: label obtained from __begin_cred_crit_section
104 * @needput: output: bool set by __begin_cred_crit_section
105 *
106 * While the cred passed to __begin is guaranteed to not change
107 * and the cred and label could be passed here instead of needput
108 * using needput with a local var makes it easier for the compiler
109 * and processor to optimize and speculatively execute the comparison
110 * than chasing a pointer in the cred struct.
111 */
__end_cred_crit_section(struct aa_label * label,bool needput)112 static inline void __end_cred_crit_section(struct aa_label *label,
113 bool needput)
114 {
115 if (unlikely(needput))
116 aa_put_label(label);
117 }
118
119 /**
120 * __begin_cred_crit_section - @cred's confining label
121 * @cred: current's cred to start a crit section on its label
122 * @needput: store whether the label needs to be put when ending crit section
123 *
124 * Returns: up to date confining label or the ns unconfined label (NOT NULL)
125 *
126 * safe to call inside locks
127 *
128 * The returned reference must be put with __end_cred_crit_section()
129 * This must NOT be used if the task cred could be updated within the
130 * critical section between
131 * __begin_cred_crit_section() .. __end_cred_crit_section()
132 *
133 * The crit section is an optimization to avoid having to get and put
134 * the newest version of the label. While the cred won't change and
135 * hence the label it contains won't change, the newest version of the
136 * label can. During the crit section the newest versions of the label
137 * will be used until the end of the crit section.
138 *
139 * If the label has not been updated at the start of the crit section
140 * no refcount is taken, the cred's refcount is enough to hold the
141 * label for the duration of the crit section.
142 *
143 * If the label has been updated then a refcount will be taken and the
144 * newest version of the label will be returned. While the cred label
145 * and the returned label could be compared at the end of the crit
146 * section, needput is used because it allows better optimization by
147 * the compiler and the processor's speculative execution.
148 */
__begin_cred_crit_section(const struct cred * cred,bool * needput)149 static inline struct aa_label *__begin_cred_crit_section(const struct cred *cred,
150 bool *needput)
151 {
152 struct aa_label *label = cred_label(cred);
153
154 if (label_is_stale(label)) {
155 *needput = true;
156 return aa_get_newest_label(label);
157 }
158
159 *needput = false;
160 return label;
161 }
162
163 /**
164 * __end_current_label_crit_section - end crit section begun with __begin_...
165 * @label: label obtained from __begin_current_label_crit_section
166 * @needput: output: bool set by __begin_current_label_crit_section
167 *
168 * wrapper around __end_cred_crit_section() to pair nicely with
169 * __begin_current_label_crit_section()
170 */
__end_current_label_crit_section(struct aa_label * label,bool needput)171 static inline void __end_current_label_crit_section(struct aa_label *label,
172 bool needput)
173 {
174 __end_cred_crit_section(label, needput);
175 }
176
177 /**
178 * end_current_label_crit_section - put a reference found with begin_current_label..
179 * @label: label reference to put
180 *
181 * Should only be used with a reference obtained with
182 * begin_current_label_crit_section and never used in situations where the
183 * task cred may be updated
184 */
end_current_label_crit_section(struct aa_label * label)185 static inline void end_current_label_crit_section(struct aa_label *label)
186 {
187 if (label != aa_current_raw_label())
188 aa_put_label(label);
189 }
190
191 /**
192 * __begin_current_label_crit_section - current's confining label
193 * @needput: store whether the label needs to be put when ending crit section
194 *
195 * Returns: up to date confining label or the ns unconfined label (NOT NULL)
196 *
197 * safe to call inside locks
198 *
199 * The returned reference must be put with __end_current_label_crit_section()
200 * This must NOT be used if the task cred could be updated within the
201 * critical section between __begin_current_label_crit_section() ..
202 * __end_current_label_crit_section()
203 */
__begin_current_label_crit_section(bool * needput)204 static inline struct aa_label *__begin_current_label_crit_section(bool *needput)
205 {
206 return __begin_cred_crit_section(current_cred(), needput);
207 }
208
209 /**
210 * begin_current_label_crit_section - current's confining label and update it
211 *
212 * Returns: up to date confining label or the ns unconfined label (NOT NULL)
213 *
214 * Not safe to call inside locks
215 *
216 * The returned reference must be put with end_current_label_crit_section()
217 * This must NOT be used if the task cred could be updated within the
218 * critical section between begin_current_label_crit_section() ..
219 * end_current_label_crit_section()
220 */
begin_current_label_crit_section(void)221 static inline struct aa_label *begin_current_label_crit_section(void)
222 {
223 struct aa_label *label = aa_current_raw_label();
224
225 might_sleep();
226
227 if (label_is_stale(label)) {
228 label = aa_get_newest_label(label);
229 if (aa_replace_current_label(label) == 0)
230 /* task cred will keep the reference */
231 aa_put_label(label);
232 }
233
234 return label;
235 }
236
aa_get_current_ns(void)237 static inline struct aa_ns *aa_get_current_ns(void)
238 {
239 struct aa_label *label;
240 struct aa_ns *ns;
241 bool needput;
242
243 label = __begin_current_label_crit_section(&needput);
244 ns = aa_get_ns(labels_ns(label));
245 __end_current_label_crit_section(label, needput);
246
247 return ns;
248 }
249
250 #endif /* __AA_CONTEXT_H */
251