xref: /openbmc/linux/security/integrity/iint.c (revision 1eb840f1)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2008 IBM Corporation
4  *
5  * Authors:
6  * Mimi Zohar <zohar@us.ibm.com>
7  *
8  * File: integrity_iint.c
9  *	- implements the integrity hooks: integrity_inode_alloc,
10  *	  integrity_inode_free
11  *	- cache integrity information associated with an inode
12  *	  using a rbtree tree.
13  */
14 #include <linux/slab.h>
15 #include <linux/init.h>
16 #include <linux/spinlock.h>
17 #include <linux/rbtree.h>
18 #include <linux/file.h>
19 #include <linux/uaccess.h>
20 #include <linux/security.h>
21 #include <linux/lsm_hooks.h>
22 #include "integrity.h"
23 
24 static struct rb_root integrity_iint_tree = RB_ROOT;
25 static DEFINE_RWLOCK(integrity_iint_lock);
26 static struct kmem_cache *iint_cache __read_mostly;
27 
28 struct dentry *integrity_dir;
29 
30 /*
31  * __integrity_iint_find - return the iint associated with an inode
32  */
__integrity_iint_find(struct inode * inode)33 static struct integrity_iint_cache *__integrity_iint_find(struct inode *inode)
34 {
35 	struct integrity_iint_cache *iint;
36 	struct rb_node *n = integrity_iint_tree.rb_node;
37 
38 	while (n) {
39 		iint = rb_entry(n, struct integrity_iint_cache, rb_node);
40 
41 		if (inode < iint->inode)
42 			n = n->rb_left;
43 		else if (inode > iint->inode)
44 			n = n->rb_right;
45 		else
46 			return iint;
47 	}
48 
49 	return NULL;
50 }
51 
52 /*
53  * integrity_iint_find - return the iint associated with an inode
54  */
integrity_iint_find(struct inode * inode)55 struct integrity_iint_cache *integrity_iint_find(struct inode *inode)
56 {
57 	struct integrity_iint_cache *iint;
58 
59 	if (!IS_IMA(inode))
60 		return NULL;
61 
62 	read_lock(&integrity_iint_lock);
63 	iint = __integrity_iint_find(inode);
64 	read_unlock(&integrity_iint_lock);
65 
66 	return iint;
67 }
68 
69 #define IMA_MAX_NESTING (FILESYSTEM_MAX_STACK_DEPTH+1)
70 
71 /*
72  * It is not clear that IMA should be nested at all, but as long is it measures
73  * files both on overlayfs and on underlying fs, we need to annotate the iint
74  * mutex to avoid lockdep false positives related to IMA + overlayfs.
75  * See ovl_lockdep_annotate_inode_mutex_key() for more details.
76  */
iint_lockdep_annotate(struct integrity_iint_cache * iint,struct inode * inode)77 static inline void iint_lockdep_annotate(struct integrity_iint_cache *iint,
78 					 struct inode *inode)
79 {
80 #ifdef CONFIG_LOCKDEP
81 	static struct lock_class_key iint_mutex_key[IMA_MAX_NESTING];
82 
83 	int depth = inode->i_sb->s_stack_depth;
84 
85 	if (WARN_ON_ONCE(depth < 0 || depth >= IMA_MAX_NESTING))
86 		depth = 0;
87 
88 	lockdep_set_class(&iint->mutex, &iint_mutex_key[depth]);
89 #endif
90 }
91 
iint_init_always(struct integrity_iint_cache * iint,struct inode * inode)92 static void iint_init_always(struct integrity_iint_cache *iint,
93 			     struct inode *inode)
94 {
95 	iint->ima_hash = NULL;
96 	iint->version = 0;
97 	iint->flags = 0UL;
98 	iint->atomic_flags = 0UL;
99 	iint->ima_file_status = INTEGRITY_UNKNOWN;
100 	iint->ima_mmap_status = INTEGRITY_UNKNOWN;
101 	iint->ima_bprm_status = INTEGRITY_UNKNOWN;
102 	iint->ima_read_status = INTEGRITY_UNKNOWN;
103 	iint->ima_creds_status = INTEGRITY_UNKNOWN;
104 	iint->evm_status = INTEGRITY_UNKNOWN;
105 	iint->measured_pcrs = 0;
106 	mutex_init(&iint->mutex);
107 	iint_lockdep_annotate(iint, inode);
108 }
109 
iint_free(struct integrity_iint_cache * iint)110 static void iint_free(struct integrity_iint_cache *iint)
111 {
112 	kfree(iint->ima_hash);
113 	mutex_destroy(&iint->mutex);
114 	kmem_cache_free(iint_cache, iint);
115 }
116 
117 /**
118  * integrity_inode_get - find or allocate an iint associated with an inode
119  * @inode: pointer to the inode
120  * @return: allocated iint
121  *
122  * Caller must lock i_mutex
123  */
integrity_inode_get(struct inode * inode)124 struct integrity_iint_cache *integrity_inode_get(struct inode *inode)
125 {
126 	struct rb_node **p;
127 	struct rb_node *node, *parent = NULL;
128 	struct integrity_iint_cache *iint, *test_iint;
129 
130 	iint = integrity_iint_find(inode);
131 	if (iint)
132 		return iint;
133 
134 	iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
135 	if (!iint)
136 		return NULL;
137 
138 	iint_init_always(iint, inode);
139 
140 	write_lock(&integrity_iint_lock);
141 
142 	p = &integrity_iint_tree.rb_node;
143 	while (*p) {
144 		parent = *p;
145 		test_iint = rb_entry(parent, struct integrity_iint_cache,
146 				     rb_node);
147 		if (inode < test_iint->inode) {
148 			p = &(*p)->rb_left;
149 		} else if (inode > test_iint->inode) {
150 			p = &(*p)->rb_right;
151 		} else {
152 			write_unlock(&integrity_iint_lock);
153 			kmem_cache_free(iint_cache, iint);
154 			return test_iint;
155 		}
156 	}
157 
158 	iint->inode = inode;
159 	node = &iint->rb_node;
160 	inode->i_flags |= S_IMA;
161 	rb_link_node(node, parent, p);
162 	rb_insert_color(node, &integrity_iint_tree);
163 
164 	write_unlock(&integrity_iint_lock);
165 	return iint;
166 }
167 
168 /**
169  * integrity_inode_free - called on security_inode_free
170  * @inode: pointer to the inode
171  *
172  * Free the integrity information(iint) associated with an inode.
173  */
integrity_inode_free(struct inode * inode)174 void integrity_inode_free(struct inode *inode)
175 {
176 	struct integrity_iint_cache *iint;
177 
178 	if (!IS_IMA(inode))
179 		return;
180 
181 	write_lock(&integrity_iint_lock);
182 	iint = __integrity_iint_find(inode);
183 	rb_erase(&iint->rb_node, &integrity_iint_tree);
184 	write_unlock(&integrity_iint_lock);
185 
186 	iint_free(iint);
187 }
188 
iint_init_once(void * foo)189 static void iint_init_once(void *foo)
190 {
191 	struct integrity_iint_cache *iint = (struct integrity_iint_cache *) foo;
192 
193 	memset(iint, 0, sizeof(*iint));
194 }
195 
integrity_iintcache_init(void)196 static int __init integrity_iintcache_init(void)
197 {
198 	iint_cache =
199 	    kmem_cache_create("iint_cache", sizeof(struct integrity_iint_cache),
200 			      0, SLAB_PANIC, iint_init_once);
201 	return 0;
202 }
203 DEFINE_LSM(integrity) = {
204 	.name = "integrity",
205 	.init = integrity_iintcache_init,
206 	.order = LSM_ORDER_LAST,
207 };
208 
209 
210 /*
211  * integrity_kernel_read - read data from the file
212  *
213  * This is a function for reading file content instead of kernel_read().
214  * It does not perform locking checks to ensure it cannot be blocked.
215  * It does not perform security checks because it is irrelevant for IMA.
216  *
217  */
integrity_kernel_read(struct file * file,loff_t offset,void * addr,unsigned long count)218 int integrity_kernel_read(struct file *file, loff_t offset,
219 			  void *addr, unsigned long count)
220 {
221 	return __kernel_read(file, addr, count, &offset);
222 }
223 
224 /*
225  * integrity_load_keys - load integrity keys hook
226  *
227  * Hooks is called from init/main.c:kernel_init_freeable()
228  * when rootfs is ready
229  */
integrity_load_keys(void)230 void __init integrity_load_keys(void)
231 {
232 	ima_load_x509();
233 
234 	if (!IS_ENABLED(CONFIG_IMA_LOAD_X509))
235 		evm_load_x509();
236 }
237 
integrity_fs_init(void)238 static int __init integrity_fs_init(void)
239 {
240 	integrity_dir = securityfs_create_dir("integrity", NULL);
241 	if (IS_ERR(integrity_dir)) {
242 		int ret = PTR_ERR(integrity_dir);
243 
244 		if (ret != -ENODEV)
245 			pr_err("Unable to create integrity sysfs dir: %d\n",
246 			       ret);
247 		integrity_dir = NULL;
248 		return ret;
249 	}
250 
251 	return 0;
252 }
253 
254 late_initcall(integrity_fs_init)
255