security/integrity/iint.c

   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 __ro_after_init;
  27
  28 struct dentry *integrity_dir;
  29
  30 /*
  31  * __integrity_iint_find - return the iint associated with an inode
  32  */
  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  */
  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  */
  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
  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
 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  */
 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  */
 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
 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
 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  */
 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  */
 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
 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)