security/integrity/ima/ima_iint.c

   1 /*
   2  * Copyright (C) 2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Mimi Zohar <zohar@us.ibm.com>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation, version 2 of the
  10  * License.
  11  *
  12  * File: ima_iint.c
  13  *      - implements the IMA hooks: ima_inode_alloc, ima_inode_free
  14  *      - cache integrity information associated with an inode
  15  *        using a rbtree tree.
  16  */
  17 #include <linux/slab.h>
  18 #include <linux/module.h>
  19 #include <linux/spinlock.h>
  20 #include <linux/rbtree.h>
  21 #include "ima.h"
  22
  23 static struct rb_root ima_iint_tree = RB_ROOT;
  24 static DEFINE_SPINLOCK(ima_iint_lock);
  25 static struct kmem_cache *iint_cache __read_mostly;
  26
  27 int iint_initialized = 0;
  28
  29 /*
  30  * __ima_iint_find - return the iint associated with an inode
  31  */
  32 static struct ima_iint_cache *__ima_iint_find(struct inode *inode)
  33 {
  34         struct ima_iint_cache *iint;
  35         struct rb_node *n = ima_iint_tree.rb_node;
  36
  37         assert_spin_locked(&ima_iint_lock);
  38
  39         while (n) {
  40                 iint = rb_entry(n, struct ima_iint_cache, rb_node);
  41
  42                 if (inode < iint->inode)
  43                         n = n->rb_left;
  44                 else if (inode > iint->inode)
  45                         n = n->rb_right;
  46                 else
  47                         break;
  48         }
  49         if (!n)
  50                 return NULL;
  51
  52         return iint;
  53 }
  54
  55 /*
  56  * ima_iint_find - return the iint associated with an inode
  57  */
  58 struct ima_iint_cache *ima_iint_find(struct inode *inode)
  59 {
  60         struct ima_iint_cache *iint;
  61
  62         if (!IS_IMA(inode))
  63                 return NULL;
  64
  65         spin_lock(&ima_iint_lock);
  66         iint = __ima_iint_find(inode);
  67         spin_unlock(&ima_iint_lock);
  68
  69         return iint;
  70 }
  71
  72 static void iint_free(struct ima_iint_cache *iint)
  73 {
  74         iint->version = 0;
  75         iint->flags = 0UL;
  76         kmem_cache_free(iint_cache, iint);
  77 }
  78
  79 /**
  80  * ima_inode_alloc - allocate an iint associated with an inode
  81  * @inode: pointer to the inode
  82  */
  83 int ima_inode_alloc(struct inode *inode)
  84 {
  85         struct rb_node **p;
  86         struct rb_node *new_node, *parent = NULL;
  87         struct ima_iint_cache *new_iint, *test_iint;
  88         int rc;
  89
  90         new_iint = kmem_cache_alloc(iint_cache, GFP_NOFS);
  91         if (!new_iint)
  92                 return -ENOMEM;
  93
  94         new_iint->inode = inode;
  95         new_node = &new_iint->rb_node;
  96
  97         mutex_lock(&inode->i_mutex); /* i_flags */
  98         spin_lock(&ima_iint_lock);
  99
 100         p = &ima_iint_tree.rb_node;
 101         while (*p) {
 102                 parent = *p;
 103                 test_iint = rb_entry(parent, struct ima_iint_cache, rb_node);
 104
 105                 rc = -EEXIST;
 106                 if (inode < test_iint->inode)
 107                         p = &(*p)->rb_left;
 108                 else if (inode > test_iint->inode)
 109                         p = &(*p)->rb_right;
 110                 else
 111                         goto out_err;
 112         }
 113
 114         inode->i_flags |= S_IMA;
 115         rb_link_node(new_node, parent, p);
 116         rb_insert_color(new_node, &ima_iint_tree);
 117
 118         spin_unlock(&ima_iint_lock);
 119         mutex_unlock(&inode->i_mutex); /* i_flags */
 120
 121         return 0;
 122 out_err:
 123         spin_unlock(&ima_iint_lock);
 124         mutex_unlock(&inode->i_mutex); /* i_flags */
 125         iint_free(new_iint);
 126
 127         return rc;
 128 }
 129
 130 /**
 131  * ima_inode_free - called on security_inode_free
 132  * @inode: pointer to the inode
 133  *
 134  * Free the integrity information(iint) associated with an inode.
 135  */
 136 void ima_inode_free(struct inode *inode)
 137 {
 138         struct ima_iint_cache *iint;
 139
 140         if (inode->i_readcount)
 141                 printk(KERN_INFO "%s: readcount: %u\n", __func__, inode->i_readcount);
 142
 143         inode->i_readcount = 0;
 144
 145         if (!IS_IMA(inode))
 146                 return;
 147
 148         spin_lock(&ima_iint_lock);
 149         iint = __ima_iint_find(inode);
 150         rb_erase(&iint->rb_node, &ima_iint_tree);
 151         spin_unlock(&ima_iint_lock);
 152
 153         iint_free(iint);
 154 }
 155
 156 static void init_once(void *foo)
 157 {
 158         struct ima_iint_cache *iint = foo;
 159
 160         memset(iint, 0, sizeof *iint);
 161         iint->version = 0;
 162         iint->flags = 0UL;
 163         mutex_init(&iint->mutex);
 164 }
 165
 166 static int __init ima_iintcache_init(void)
 167 {
 168         iint_cache =
 169             kmem_cache_create("iint_cache", sizeof(struct ima_iint_cache), 0,
 170                               SLAB_PANIC, init_once);
 171         iint_initialized = 1;
 172         return 0;
 173 }
 174 security_initcall(ima_iintcache_init);