security/tomoyo/gc.c

   1 /*
   2  * security/tomoyo/gc.c
   3  *
   4  * Implementation of the Domain-Based Mandatory Access Control.
   5  *
   6  * Copyright (C) 2005-2010  NTT DATA CORPORATION
   7  *
   8  */
   9
  10 #include "common.h"
  11 #include <linux/kthread.h>
  12 #include <linux/slab.h>
  13
  14 enum tomoyo_gc_id {
  15         TOMOYO_ID_DOMAIN_INITIALIZER,
  16         TOMOYO_ID_DOMAIN_KEEPER,
  17         TOMOYO_ID_ALIAS,
  18         TOMOYO_ID_GLOBALLY_READABLE,
  19         TOMOYO_ID_PATTERN,
  20         TOMOYO_ID_NO_REWRITE,
  21         TOMOYO_ID_MANAGER,
  22         TOMOYO_ID_NAME,
  23         TOMOYO_ID_ACL,
  24         TOMOYO_ID_DOMAIN
  25 };
  26
  27 struct tomoyo_gc_entry {
  28         struct list_head list;
  29         int type;
  30         void *element;
  31 };
  32 static LIST_HEAD(tomoyo_gc_queue);
  33 static DEFINE_MUTEX(tomoyo_gc_mutex);
  34
  35 /* Caller holds tomoyo_policy_lock mutex. */
  36 static bool tomoyo_add_to_gc(const int type, void *element)
  37 {
  38         struct tomoyo_gc_entry *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
  39         if (!entry)
  40                 return false;
  41         entry->type = type;
  42         entry->element = element;
  43         list_add(&entry->list, &tomoyo_gc_queue);
  44         return true;
  45 }
  46
  47 static void tomoyo_del_allow_read
  48 (struct tomoyo_globally_readable_file_entry *ptr)
  49 {
  50         tomoyo_put_name(ptr->filename);
  51 }
  52
  53 static void tomoyo_del_file_pattern(struct tomoyo_pattern_entry *ptr)
  54 {
  55         tomoyo_put_name(ptr->pattern);
  56 }
  57
  58 static void tomoyo_del_no_rewrite(struct tomoyo_no_rewrite_entry *ptr)
  59 {
  60         tomoyo_put_name(ptr->pattern);
  61 }
  62
  63 static void tomoyo_del_domain_initializer
  64 (struct tomoyo_domain_initializer_entry *ptr)
  65 {
  66         tomoyo_put_name(ptr->domainname);
  67         tomoyo_put_name(ptr->program);
  68 }
  69
  70 static void tomoyo_del_domain_keeper(struct tomoyo_domain_keeper_entry *ptr)
  71 {
  72         tomoyo_put_name(ptr->domainname);
  73         tomoyo_put_name(ptr->program);
  74 }
  75
  76 static void tomoyo_del_alias(struct tomoyo_alias_entry *ptr)
  77 {
  78         tomoyo_put_name(ptr->original_name);
  79         tomoyo_put_name(ptr->aliased_name);
  80 }
  81
  82 static void tomoyo_del_manager(struct tomoyo_policy_manager_entry *ptr)
  83 {
  84         tomoyo_put_name(ptr->manager);
  85 }
  86
  87 static void tomoyo_del_acl(struct tomoyo_acl_info *acl)
  88 {
  89         switch (acl->type) {
  90         case TOMOYO_TYPE_PATH_ACL:
  91                 {
  92                         struct tomoyo_path_acl *entry
  93                                 = container_of(acl, typeof(*entry), head);
  94                         tomoyo_put_name(entry->filename);
  95                 }
  96                 break;
  97         case TOMOYO_TYPE_PATH2_ACL:
  98                 {
  99                         struct tomoyo_path2_acl *entry
 100                                 = container_of(acl, typeof(*entry), head);
 101                         tomoyo_put_name(entry->filename1);
 102                         tomoyo_put_name(entry->filename2);
 103                 }
 104                 break;
 105         default:
 106                 printk(KERN_WARNING "Unknown type\n");
 107                 break;
 108         }
 109 }
 110
 111 static bool tomoyo_del_domain(struct tomoyo_domain_info *domain)
 112 {
 113         struct tomoyo_acl_info *acl;
 114         struct tomoyo_acl_info *tmp;
 115         /*
 116          * Since we don't protect whole execve() operation using SRCU,
 117          * we need to recheck domain->users at this point.
 118          *
 119          * (1) Reader starts SRCU section upon execve().
 120          * (2) Reader traverses tomoyo_domain_list and finds this domain.
 121          * (3) Writer marks this domain as deleted.
 122          * (4) Garbage collector removes this domain from tomoyo_domain_list
 123          *     because this domain is marked as deleted and used by nobody.
 124          * (5) Reader saves reference to this domain into
 125          *     "struct linux_binprm"->cred->security .
 126          * (6) Reader finishes SRCU section, although execve() operation has
 127          *     not finished yet.
 128          * (7) Garbage collector waits for SRCU synchronization.
 129          * (8) Garbage collector kfree() this domain because this domain is
 130          *     used by nobody.
 131          * (9) Reader finishes execve() operation and restores this domain from
 132          *     "struct linux_binprm"->cred->security.
 133          *
 134          * By updating domain->users at (5), we can solve this race problem
 135          * by rechecking domain->users at (8).
 136          */
 137         if (atomic_read(&domain->users))
 138                 return false;
 139         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
 140                 tomoyo_del_acl(acl);
 141                 tomoyo_memory_free(acl);
 142         }
 143         tomoyo_put_name(domain->domainname);
 144         return true;
 145 }
 146
 147
 148 static void tomoyo_del_name(const struct tomoyo_name_entry *ptr)
 149 {
 150 }
 151
 152 static void tomoyo_collect_entry(void)
 153 {
 154         if (mutex_lock_interruptible(&tomoyo_policy_lock))
 155                 return;
 156         {
 157                 struct tomoyo_globally_readable_file_entry *ptr;
 158                 list_for_each_entry_rcu(ptr, &tomoyo_globally_readable_list,
 159                                         list) {
 160                         if (!ptr->is_deleted)
 161                                 continue;
 162                         if (tomoyo_add_to_gc(TOMOYO_ID_GLOBALLY_READABLE, ptr))
 163                                 list_del_rcu(&ptr->list);
 164                         else
 165                                 break;
 166                 }
 167         }
 168         {
 169                 struct tomoyo_pattern_entry *ptr;
 170                 list_for_each_entry_rcu(ptr, &tomoyo_pattern_list, list) {
 171                         if (!ptr->is_deleted)
 172                                 continue;
 173                         if (tomoyo_add_to_gc(TOMOYO_ID_PATTERN, ptr))
 174                                 list_del_rcu(&ptr->list);
 175                         else
 176                                 break;
 177                 }
 178         }
 179         {
 180                 struct tomoyo_no_rewrite_entry *ptr;
 181                 list_for_each_entry_rcu(ptr, &tomoyo_no_rewrite_list, list) {
 182                         if (!ptr->is_deleted)
 183                                 continue;
 184                         if (tomoyo_add_to_gc(TOMOYO_ID_NO_REWRITE, ptr))
 185                                 list_del_rcu(&ptr->list);
 186                         else
 187                                 break;
 188                 }
 189         }
 190         {
 191                 struct tomoyo_domain_initializer_entry *ptr;
 192                 list_for_each_entry_rcu(ptr, &tomoyo_domain_initializer_list,
 193                                         list) {
 194                         if (!ptr->is_deleted)
 195                                 continue;
 196                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN_INITIALIZER, ptr))
 197                                 list_del_rcu(&ptr->list);
 198                         else
 199                                 break;
 200                 }
 201         }
 202         {
 203                 struct tomoyo_domain_keeper_entry *ptr;
 204                 list_for_each_entry_rcu(ptr, &tomoyo_domain_keeper_list, list) {
 205                         if (!ptr->is_deleted)
 206                                 continue;
 207                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN_KEEPER, ptr))
 208                                 list_del_rcu(&ptr->list);
 209                         else
 210                                 break;
 211                 }
 212         }
 213         {
 214                 struct tomoyo_alias_entry *ptr;
 215                 list_for_each_entry_rcu(ptr, &tomoyo_alias_list, list) {
 216                         if (!ptr->is_deleted)
 217                                 continue;
 218                         if (tomoyo_add_to_gc(TOMOYO_ID_ALIAS, ptr))
 219                                 list_del_rcu(&ptr->list);
 220                         else
 221                                 break;
 222                 }
 223         }
 224         {
 225                 struct tomoyo_policy_manager_entry *ptr;
 226                 list_for_each_entry_rcu(ptr, &tomoyo_policy_manager_list,
 227                                         list) {
 228                         if (!ptr->is_deleted)
 229                                 continue;
 230                         if (tomoyo_add_to_gc(TOMOYO_ID_MANAGER, ptr))
 231                                 list_del_rcu(&ptr->list);
 232                         else
 233                                 break;
 234                 }
 235         }
 236         {
 237                 struct tomoyo_domain_info *domain;
 238                 list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
 239                         struct tomoyo_acl_info *acl;
 240                         list_for_each_entry_rcu(acl, &domain->acl_info_list,
 241                                                 list) {
 242                                 switch (acl->type) {
 243                                 case TOMOYO_TYPE_PATH_ACL:
 244                                         if (container_of(acl,
 245                                          struct tomoyo_path_acl,
 246                                                          head)->perm ||
 247                                             container_of(acl,
 248                                          struct tomoyo_path_acl,
 249                                                          head)->perm_high)
 250                                                 continue;
 251                                         break;
 252                                 case TOMOYO_TYPE_PATH2_ACL:
 253                                         if (container_of(acl,
 254                                          struct tomoyo_path2_acl,
 255                                                          head)->perm)
 256                                                 continue;
 257                                         break;
 258                                 default:
 259                                         continue;
 260                                 }
 261                                 if (tomoyo_add_to_gc(TOMOYO_ID_ACL, acl))
 262                                         list_del_rcu(&acl->list);
 263                                 else
 264                                         break;
 265                         }
 266                         if (!domain->is_deleted || atomic_read(&domain->users))
 267                                 continue;
 268                         /*
 269                          * Nobody is referring this domain. But somebody may
 270                          * refer this domain after successful execve().
 271                          * We recheck domain->users after SRCU synchronization.
 272                          */
 273                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, domain))
 274                                 list_del_rcu(&domain->list);
 275                         else
 276                                 break;
 277                 }
 278         }
 279         {
 280                 int i;
 281                 for (i = 0; i < TOMOYO_MAX_HASH; i++) {
 282                         struct tomoyo_name_entry *ptr;
 283                         list_for_each_entry_rcu(ptr, &tomoyo_name_list[i],
 284                                                 list) {
 285                                 if (atomic_read(&ptr->users))
 286                                         continue;
 287                                 if (tomoyo_add_to_gc(TOMOYO_ID_NAME, ptr))
 288                                         list_del_rcu(&ptr->list);
 289                                 else {
 290                                         i = TOMOYO_MAX_HASH;
 291                                         break;
 292                                 }
 293                         }
 294                 }
 295         }
 296         mutex_unlock(&tomoyo_policy_lock);
 297 }
 298
 299 static void tomoyo_kfree_entry(void)
 300 {
 301         struct tomoyo_gc_entry *p;
 302         struct tomoyo_gc_entry *tmp;
 303
 304         list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) {
 305                 switch (p->type) {
 306                 case TOMOYO_ID_DOMAIN_INITIALIZER:
 307                         tomoyo_del_domain_initializer(p->element);
 308                         break;
 309                 case TOMOYO_ID_DOMAIN_KEEPER:
 310                         tomoyo_del_domain_keeper(p->element);
 311                         break;
 312                 case TOMOYO_ID_ALIAS:
 313                         tomoyo_del_alias(p->element);
 314                         break;
 315                 case TOMOYO_ID_GLOBALLY_READABLE:
 316                         tomoyo_del_allow_read(p->element);
 317                         break;
 318                 case TOMOYO_ID_PATTERN:
 319                         tomoyo_del_file_pattern(p->element);
 320                         break;
 321                 case TOMOYO_ID_NO_REWRITE:
 322                         tomoyo_del_no_rewrite(p->element);
 323                         break;
 324                 case TOMOYO_ID_MANAGER:
 325                         tomoyo_del_manager(p->element);
 326                         break;
 327                 case TOMOYO_ID_NAME:
 328                         tomoyo_del_name(p->element);
 329                         break;
 330                 case TOMOYO_ID_ACL:
 331                         tomoyo_del_acl(p->element);
 332                         break;
 333                 case TOMOYO_ID_DOMAIN:
 334                         if (!tomoyo_del_domain(p->element))
 335                                 continue;
 336                         break;
 337                 default:
 338                         printk(KERN_WARNING "Unknown type\n");
 339                         break;
 340                 }
 341                 tomoyo_memory_free(p->element);
 342                 list_del(&p->list);
 343                 kfree(p);
 344         }
 345 }
 346
 347 static int tomoyo_gc_thread(void *unused)
 348 {
 349         daemonize("GC for TOMOYO");
 350         if (mutex_trylock(&tomoyo_gc_mutex)) {
 351                 int i;
 352                 for (i = 0; i < 10; i++) {
 353                         tomoyo_collect_entry();
 354                         if (list_empty(&tomoyo_gc_queue))
 355                                 break;
 356                         synchronize_srcu(&tomoyo_ss);
 357                         tomoyo_kfree_entry();
 358                 }
 359                 mutex_unlock(&tomoyo_gc_mutex);
 360         }
 361         do_exit(0);
 362 }
 363
 364 void tomoyo_run_gc(void)
 365 {
 366         struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
 367                                                   "GC for TOMOYO");
 368         if (!IS_ERR(task))
 369                 wake_up_process(task);
 370 }