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
 24static struct rb_root integrity_iint_tree = RB_ROOT;
 25static DEFINE_RWLOCK(integrity_iint_lock);
 26static struct kmem_cache *iint_cache __ro_after_init;
 27
 28struct dentry *integrity_dir;
 29
 30/*
 31 * __integrity_iint_find - return the iint associated with an inode
 32 */
 33static 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 */
 55struct 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 */
 77static 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
 92static 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
110static 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 */
124struct 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 */
174void 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
189static 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
196static 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}
203DEFINE_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 */
218int 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 */
230void __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
238static 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
254late_initcall(integrity_fs_init)