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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Landlock LSM - Ruleset management
4 *
5 * Copyright © 2016-2020 Mickaël Salaün <[email protected]>
6 * Copyright © 2018-2020 ANSSI
7 * Copyright © 2026 Cloudflare, Inc.
8 */
9
10#include <linux/bits.h>
11#include <linux/bug.h>
12#include <linux/cleanup.h>
13#include <linux/compiler_types.h>
14#include <linux/err.h>
15#include <linux/errno.h>
16#include <linux/kernel.h>
17#include <linux/lockdep.h>
18#include <linux/mutex.h>
19#include <linux/overflow.h>
20#include <linux/rbtree.h>
21#include <linux/refcount.h>
22#include <linux/slab.h>
23#include <linux/spinlock.h>
24#include <uapi/linux/landlock.h>
25
26#include "access.h"
27#include "id.h"
28#include "limits.h"
29#include "object.h"
30#include "ruleset.h"
31
32#include <trace/events/landlock.h>
33
34struct landlock_ruleset *
35landlock_create_ruleset(const access_mask_t fs_access_mask,
36 const access_mask_t net_access_mask,
37 const access_mask_t scope_mask)
38{
39 struct landlock_ruleset *new_ruleset;
40
41 /* Informs about useless ruleset. */
42 if (!fs_access_mask && !net_access_mask && !scope_mask)
43 return ERR_PTR(-ENOMSG);
44
45 new_ruleset = kzalloc_obj(*new_ruleset, GFP_KERNEL_ACCOUNT);
46 if (!new_ruleset)
47 return ERR_PTR(-ENOMEM);
48
49 refcount_set(&new_ruleset->usage, 1);
50 mutex_init(&new_ruleset->lock);
51 new_ruleset->rules.root_inode = RB_ROOT;
52
53#if IS_ENABLED(CONFIG_INET)
54 new_ruleset->rules.root_net_port = RB_ROOT;
55#endif /* IS_ENABLED(CONFIG_INET) */
56
57#ifdef CONFIG_TRACEPOINTS
58 new_ruleset->id = landlock_get_id_range(1);
59#endif /* CONFIG_TRACEPOINTS */
60
61 /* The caller must only pass supported access rights and scopes. */
62 if (fs_access_mask) {
63 const access_mask_t mask = fs_access_mask &
64 LANDLOCK_MASK_ACCESS_FS;
65
66 WARN_ON_ONCE(fs_access_mask != mask);
67 new_ruleset->handled_masks.fs |= mask;
68 }
69 if (net_access_mask) {
70 const access_mask_t mask = net_access_mask &
71 LANDLOCK_MASK_ACCESS_NET;
72
73 WARN_ON_ONCE(net_access_mask != mask);
74 new_ruleset->handled_masks.net |= mask;
75 }
76 if (scope_mask) {
77 const access_mask_t mask = scope_mask & LANDLOCK_MASK_SCOPE;
78
79 WARN_ON_ONCE(scope_mask != mask);
80 new_ruleset->handled_masks.scope |= mask;
81 }
82 return new_ruleset;
83}
84
85static void build_check_rule(void)
86{
87 const struct landlock_rule rule = {
88 .num_layers = ~0,
89 };
90
91 /*
92 * Checks that .num_layers is large enough for at least
93 * LANDLOCK_MAX_NUM_LAYERS layers.
94 */
95 BUILD_BUG_ON(rule.num_layers < LANDLOCK_MAX_NUM_LAYERS);
96}
97
98static bool is_object_pointer(const enum landlock_key_type key_type)
99{
100 switch (key_type) {
101 case LANDLOCK_KEY_INODE:
102 return true;
103
104#if IS_ENABLED(CONFIG_INET)
105 case LANDLOCK_KEY_NET_PORT:
106 return false;
107#endif /* IS_ENABLED(CONFIG_INET) */
108
109 default:
110 WARN_ON_ONCE(1);
111 return false;
112 }
113}
114
115static struct landlock_rule *
116create_rule(const struct landlock_id id,
117 const struct landlock_layer (*layers)[], const u32 num_layers,
118 const struct landlock_layer *const new_layer)
119{
120 struct landlock_rule *new_rule;
121 u32 new_num_layers;
122
123 build_check_rule();
124 if (new_layer) {
125 /* Should already be checked by landlock_merge_ruleset(). */
126 if (WARN_ON_ONCE(num_layers >= LANDLOCK_MAX_NUM_LAYERS))
127 return ERR_PTR(-E2BIG);
128 new_num_layers = num_layers + 1;
129 } else {
130 new_num_layers = num_layers;
131 }
132 new_rule = kzalloc_flex(*new_rule, layers, new_num_layers,
133 GFP_KERNEL_ACCOUNT);
134 if (!new_rule)
135 return ERR_PTR(-ENOMEM);
136 RB_CLEAR_NODE(&new_rule->node);
137 if (is_object_pointer(id.type)) {
138 /* This should have been caught by landlock_store_rule(). */
139 WARN_ON_ONCE(!id.key.object);
140 landlock_get_object(id.key.object);
141 }
142
143 new_rule->key = id.key;
144 new_rule->num_layers = new_num_layers;
145 /* Copies the original layer stack. */
146 memcpy(new_rule->layers, layers,
147 flex_array_size(new_rule, layers, num_layers));
148 if (new_layer)
149 /* Adds a copy of @new_layer on the layer stack. */
150 new_rule->layers[new_rule->num_layers - 1] = *new_layer;
151 return new_rule;
152}
153
154static void free_rule(struct landlock_rule *const rule,
155 const enum landlock_key_type key_type)
156{
157 might_sleep();
158 if (!rule)
159 return;
160 if (is_object_pointer(key_type))
161 landlock_put_object(rule->key.object);
162 kfree(rule);
163}
164
165static void build_check_ruleset(void)
166{
167 const struct landlock_rules rules = {
168 .num_rules = ~0,
169 };
170
171 BUILD_BUG_ON(rules.num_rules < LANDLOCK_MAX_NUM_RULES);
172}
173
174/**
175 * landlock_store_rule - Create and insert a rule into the rule storage
176 *
177 * @rules: The rule storage to be updated. The caller is responsible for
178 * any required locking. For rulesets, this means holding
179 * &landlock_ruleset.lock. For domains under construction, no lock is
180 * needed because the domain is not yet visible to other tasks.
181 * @id: The ID to build the new rule with. The underlying kernel object, if
182 * any, must be held by the caller.
183 * @layers: One or multiple layers to be copied into the new rule.
184 * @num_layers: The number of @layers entries.
185 *
186 * When user space requests to add a new rule to a ruleset, @layers only
187 * contains one entry and this entry is not assigned to any level. In this
188 * case, the new rule will extend @rules, similarly to a boolean OR between
189 * access rights.
190 *
191 * When merging a ruleset in a domain, or copying a domain, @layers will be
192 * added to @rules as new constraints, similarly to a boolean AND between access
193 * rights.
194 *
195 * Return: 0 on success, -errno on failure.
196 */
197int landlock_store_rule(struct landlock_rules *const rules,
198 const struct landlock_id id,
199 const struct landlock_layer (*layers)[],
200 const size_t num_layers)
201{
202 struct rb_node **walker_node;
203 struct rb_node *parent_node = NULL;
204 struct landlock_rule *new_rule;
205 struct rb_root *root;
206
207 might_sleep();
208 if (WARN_ON_ONCE(!layers))
209 return -ENOENT;
210
211 if (is_object_pointer(id.type) && WARN_ON_ONCE(!id.key.object))
212 return -ENOENT;
213
214 root = landlock_get_rule_root(rules, id.type);
215 if (IS_ERR(root))
216 return PTR_ERR(root);
217
218 walker_node = &root->rb_node;
219 while (*walker_node) {
220 struct landlock_rule *const this =
221 rb_entry(*walker_node, struct landlock_rule, node);
222
223 if (this->key.data != id.key.data) {
224 parent_node = *walker_node;
225 if (this->key.data < id.key.data)
226 walker_node = &((*walker_node)->rb_right);
227 else
228 walker_node = &((*walker_node)->rb_left);
229 continue;
230 }
231
232 /* Only a single-level layer should match an existing rule. */
233 if (WARN_ON_ONCE(num_layers != 1))
234 return -EINVAL;
235
236 /* If there is a matching rule, updates it. */
237 if ((*layers)[0].level == 0) {
238 /*
239 * Extends access rights when the request comes from
240 * landlock_add_rule(2), i.e. @rules is not a domain.
241 */
242 if (WARN_ON_ONCE(this->num_layers != 1))
243 return -EINVAL;
244 if (WARN_ON_ONCE(this->layers[0].level != 0))
245 return -EINVAL;
246 this->layers[0].access |= (*layers)[0].access;
247 this->layers[0].flags.quiet |= (*layers)[0].flags.quiet;
248 return 0;
249 }
250
251 if (WARN_ON_ONCE(this->layers[0].level == 0))
252 return -EINVAL;
253
254 /*
255 * Intersects access rights when it is a merge between a
256 * ruleset and a domain.
257 */
258 new_rule = create_rule(id, &this->layers, this->num_layers,
259 &(*layers)[0]);
260 if (IS_ERR(new_rule))
261 return PTR_ERR(new_rule);
262 rb_replace_node(&this->node, &new_rule->node, root);
263 free_rule(this, id.type);
264 return 0;
265 }
266
267 /* There is no match for @id. */
268 build_check_ruleset();
269 if (rules->num_rules >= LANDLOCK_MAX_NUM_RULES)
270 return -E2BIG;
271 new_rule = create_rule(id, layers, num_layers, NULL);
272 if (IS_ERR(new_rule))
273 return PTR_ERR(new_rule);
274 rb_link_node(&new_rule->node, parent_node, walker_node);
275 rb_insert_color(&new_rule->node, root);
276 rules->num_rules++;
277 return 0;
278}
279
280static void build_check_layer(void)
281{
282 const struct landlock_layer layer = {
283 .level = ~0,
284 .access = ~0,
285 };
286
287 /*
288 * Checks that .level and .access are large enough to contain their expected
289 * maximum values.
290 */
291 BUILD_BUG_ON(layer.level < LANDLOCK_MAX_NUM_LAYERS);
292 BUILD_BUG_ON(layer.access < LANDLOCK_MASK_ACCESS_FS);
293}
294
295/* @ruleset must be locked by the caller. */
296int landlock_insert_rule(struct landlock_ruleset *const ruleset,
297 const struct landlock_id id,
298 const access_mask_t access, const u32 flags)
299{
300 struct landlock_layer layers[] = { {
301 .access = access,
302 /*
303 * When @level is zero, landlock_store_rule() extends @ruleset.
304 */
305 .level = 0,
306 .flags = {
307 .quiet = !!(flags & LANDLOCK_ADD_RULE_QUIET),
308 },
309 } };
310 int err;
311
312 build_check_layer();
313 lockdep_assert_held(&ruleset->lock);
314 err = landlock_store_rule(&ruleset->rules, id, &layers,
315 ARRAY_SIZE(layers));
316
317#ifdef CONFIG_TRACEPOINTS
318 if (!err)
319 ruleset->version++;
320#endif /* CONFIG_TRACEPOINTS */
321
322 return err;
323}
324
325void landlock_free_rules(struct landlock_rules *const rules)
326{
327 struct landlock_rule *freeme, *next;
328
329 might_sleep();
330 rbtree_postorder_for_each_entry_safe(freeme, next, &rules->root_inode,
331 node)
332 free_rule(freeme, LANDLOCK_KEY_INODE);
333
334#if IS_ENABLED(CONFIG_INET)
335 rbtree_postorder_for_each_entry_safe(freeme, next,
336 &rules->root_net_port, node)
337 free_rule(freeme, LANDLOCK_KEY_NET_PORT);
338#endif /* IS_ENABLED(CONFIG_INET) */
339}
340
341static void free_ruleset(struct landlock_ruleset *const ruleset)
342{
343 might_sleep();
344 trace_landlock_free_ruleset(ruleset);
345 landlock_free_rules(&ruleset->rules);
346 kfree(ruleset);
347}
348
349void landlock_put_ruleset(struct landlock_ruleset *const ruleset)
350{
351 might_sleep();
352 if (ruleset && refcount_dec_and_test(&ruleset->usage))
353 free_ruleset(ruleset);
354}