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_PATH_GROUP,
  16         TOMOYO_ID_PATH_GROUP_MEMBER,
  17         TOMOYO_ID_DOMAIN_INITIALIZER,
  18         TOMOYO_ID_DOMAIN_KEEPER,
  19         TOMOYO_ID_ALIAS,
  20         TOMOYO_ID_GLOBALLY_READABLE,
  21         TOMOYO_ID_PATTERN,
  22         TOMOYO_ID_NO_REWRITE,
  23         TOMOYO_ID_MANAGER,
  24         TOMOYO_ID_NAME,
  25         TOMOYO_ID_ACL,
  26         TOMOYO_ID_DOMAIN
  27 };
  28
  29 struct tomoyo_gc_entry {
  30         struct list_head list;
  31         int type;
  32         void *element;
  33 };
  34 static LIST_HEAD(tomoyo_gc_queue);
  35 static DEFINE_MUTEX(tomoyo_gc_mutex);
  36
  37 /* Caller holds tomoyo_policy_lock mutex. */
  38 static bool tomoyo_add_to_gc(const int type, void *element)
  39 {
  40         struct tomoyo_gc_entry *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
  41         if (!entry)
  42                 return false;
  43         entry->type = type;
  44         entry->element = element;
  45         list_add(&entry->list, &tomoyo_gc_queue);
  46         return true;
  47 }
  48
  49 static void tomoyo_del_allow_read
  50 (struct tomoyo_globally_readable_file_entry *ptr)
  51 {
  52         tomoyo_put_name(ptr->filename);
  53 }
  54
  55 static void tomoyo_del_file_pattern(struct tomoyo_pattern_entry *ptr)
  56 {
  57         tomoyo_put_name(ptr->pattern);
  58 }
  59
  60 static void tomoyo_del_no_rewrite(struct tomoyo_no_rewrite_entry *ptr)
  61 {
  62         tomoyo_put_name(ptr->pattern);
  63 }
  64
  65 static void tomoyo_del_domain_initializer
  66 (struct tomoyo_domain_initializer_entry *ptr)
  67 {
  68         tomoyo_put_name(ptr->domainname);
  69         tomoyo_put_name(ptr->program);
  70 }
  71
  72 static void tomoyo_del_domain_keeper(struct tomoyo_domain_keeper_entry *ptr)
  73 {
  74         tomoyo_put_name(ptr->domainname);
  75         tomoyo_put_name(ptr->program);
  76 }
  77
  78 static void tomoyo_del_alias(struct tomoyo_alias_entry *ptr)
  79 {
  80         tomoyo_put_name(ptr->original_name);
  81         tomoyo_put_name(ptr->aliased_name);
  82 }
  83
  84 static void tomoyo_del_manager(struct tomoyo_policy_manager_entry *ptr)
  85 {
  86         tomoyo_put_name(ptr->manager);
  87 }
  88
  89 static void tomoyo_del_acl(struct tomoyo_acl_info *acl)
  90 {
  91         switch (acl->type) {
  92         case TOMOYO_TYPE_PATH_ACL:
  93                 {
  94                         struct tomoyo_path_acl *entry
  95                                 = container_of(acl, typeof(*entry), head);
  96                         tomoyo_put_name_union(&entry->name);
  97                 }
  98                 break;
  99         case TOMOYO_TYPE_PATH2_ACL:
 100                 {
 101                         struct tomoyo_path2_acl *entry
 102                                 = container_of(acl, typeof(*entry), head);
 103                         tomoyo_put_name_union(&entry->name1);
 104                         tomoyo_put_name_union(&entry->name2);
 105                 }
 106                 break;
 107         default:
 108                 printk(KERN_WARNING "Unknown type\n");
 109                 break;
 110         }
 111 }
 112
 113 static bool tomoyo_del_domain(struct tomoyo_domain_info *domain)
 114 {
 115         struct tomoyo_acl_info *acl;
 116         struct tomoyo_acl_info *tmp;
 117         /*
 118          * Since we don't protect whole execve() operation using SRCU,
 119          * we need to recheck domain->users at this point.
 120          *
 121          * (1) Reader starts SRCU section upon execve().
 122          * (2) Reader traverses tomoyo_domain_list and finds this domain.
 123          * (3) Writer marks this domain as deleted.
 124          * (4) Garbage collector removes this domain from tomoyo_domain_list
 125          *     because this domain is marked as deleted and used by nobody.
 126          * (5) Reader saves reference to this domain into
 127          *     "struct linux_binprm"->cred->security .
 128          * (6) Reader finishes SRCU section, although execve() operation has
 129          *     not finished yet.
 130          * (7) Garbage collector waits for SRCU synchronization.
 131          * (8) Garbage collector kfree() this domain because this domain is
 132          *     used by nobody.
 133          * (9) Reader finishes execve() operation and restores this domain from
 134          *     "struct linux_binprm"->cred->security.
 135          *
 136          * By updating domain->users at (5), we can solve this race problem
 137          * by rechecking domain->users at (8).
 138          */
 139         if (atomic_read(&domain->users))
 140                 return false;
 141         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
 142                 tomoyo_del_acl(acl);
 143                 tomoyo_memory_free(acl);
 144         }
 145         tomoyo_put_name(domain->domainname);
 146         return true;
 147 }
 148
 149
 150 static void tomoyo_del_name(const struct tomoyo_name_entry *ptr)
 151 {
 152 }
 153
 154 static void tomoyo_del_path_group_member(struct tomoyo_path_group_member
 155                                          *member)
 156 {
 157         tomoyo_put_name(member->member_name);
 158 }
 159
 160 static void tomoyo_del_path_group(struct tomoyo_path_group *group)
 161 {
 162         tomoyo_put_name(group->group_name);
 163 }
 164
 165 static void tomoyo_collect_entry(void)
 166 {
 167         if (mutex_lock_interruptible(&tomoyo_policy_lock))
 168                 return;
 169         {
 170                 struct tomoyo_globally_readable_file_entry *ptr;
 171                 list_for_each_entry_rcu(ptr, &tomoyo_globally_readable_list,
 172                                         list) {
 173                         if (!ptr->is_deleted)
 174                                 continue;
 175                         if (tomoyo_add_to_gc(TOMOYO_ID_GLOBALLY_READABLE, ptr))
 176                                 list_del_rcu(&ptr->list);
 177                         else
 178                                 break;
 179                 }
 180         }
 181         {
 182                 struct tomoyo_pattern_entry *ptr;
 183                 list_for_each_entry_rcu(ptr, &tomoyo_pattern_list, list) {
 184                         if (!ptr->is_deleted)
 185                                 continue;
 186                         if (tomoyo_add_to_gc(TOMOYO_ID_PATTERN, ptr))
 187                                 list_del_rcu(&ptr->list);
 188                         else
 189                                 break;
 190                 }
 191         }
 192         {
 193                 struct tomoyo_no_rewrite_entry *ptr;
 194                 list_for_each_entry_rcu(ptr, &tomoyo_no_rewrite_list, list) {
 195                         if (!ptr->is_deleted)
 196                                 continue;
 197                         if (tomoyo_add_to_gc(TOMOYO_ID_NO_REWRITE, ptr))
 198                                 list_del_rcu(&ptr->list);
 199                         else
 200                                 break;
 201                 }
 202         }
 203         {
 204                 struct tomoyo_domain_initializer_entry *ptr;
 205                 list_for_each_entry_rcu(ptr, &tomoyo_domain_initializer_list,
 206                                         list) {
 207                         if (!ptr->is_deleted)
 208                                 continue;
 209                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN_INITIALIZER, ptr))
 210                                 list_del_rcu(&ptr->list);
 211                         else
 212                                 break;
 213                 }
 214         }
 215         {
 216                 struct tomoyo_domain_keeper_entry *ptr;
 217                 list_for_each_entry_rcu(ptr, &tomoyo_domain_keeper_list, list) {
 218                         if (!ptr->is_deleted)
 219                                 continue;
 220                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN_KEEPER, ptr))
 221                                 list_del_rcu(&ptr->list);
 222                         else
 223                                 break;
 224                 }
 225         }
 226         {
 227                 struct tomoyo_alias_entry *ptr;
 228                 list_for_each_entry_rcu(ptr, &tomoyo_alias_list, list) {
 229                         if (!ptr->is_deleted)
 230                                 continue;
 231                         if (tomoyo_add_to_gc(TOMOYO_ID_ALIAS, ptr))
 232                                 list_del_rcu(&ptr->list);
 233                         else
 234                                 break;
 235                 }
 236         }
 237         {
 238                 struct tomoyo_policy_manager_entry *ptr;
 239                 list_for_each_entry_rcu(ptr, &tomoyo_policy_manager_list,
 240                                         list) {
 241                         if (!ptr->is_deleted)
 242                                 continue;
 243                         if (tomoyo_add_to_gc(TOMOYO_ID_MANAGER, ptr))
 244                                 list_del_rcu(&ptr->list);
 245                         else
 246                                 break;
 247                 }
 248         }
 249         {
 250                 struct tomoyo_domain_info *domain;
 251                 list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
 252                         struct tomoyo_acl_info *acl;
 253                         list_for_each_entry_rcu(acl, &domain->acl_info_list,
 254                                                 list) {
 255                                 switch (acl->type) {
 256                                 case TOMOYO_TYPE_PATH_ACL:
 257                                         if (container_of(acl,
 258                                          struct tomoyo_path_acl,
 259                                                          head)->perm ||
 260                                             container_of(acl,
 261                                          struct tomoyo_path_acl,
 262                                                          head)->perm_high)
 263                                                 continue;
 264                                         break;
 265                                 case TOMOYO_TYPE_PATH2_ACL:
 266                                         if (container_of(acl,
 267                                          struct tomoyo_path2_acl,
 268                                                          head)->perm)
 269                                                 continue;
 270                                         break;
 271                                 default:
 272                                         continue;
 273                                 }
 274                                 if (tomoyo_add_to_gc(TOMOYO_ID_ACL, acl))
 275                                         list_del_rcu(&acl->list);
 276                                 else
 277                                         break;
 278                         }
 279                         if (!domain->is_deleted || atomic_read(&domain->users))
 280                                 continue;
 281                         /*
 282                          * Nobody is referring this domain. But somebody may
 283                          * refer this domain after successful execve().
 284                          * We recheck domain->users after SRCU synchronization.
 285                          */
 286                         if (tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, domain))
 287                                 list_del_rcu(&domain->list);
 288                         else
 289                                 break;
 290                 }
 291         }
 292         {
 293                 int i;
 294                 for (i = 0; i < TOMOYO_MAX_HASH; i++) {
 295                         struct tomoyo_name_entry *ptr;
 296                         list_for_each_entry_rcu(ptr, &tomoyo_name_list[i],
 297                                                 list) {
 298                                 if (atomic_read(&ptr->users))
 299                                         continue;
 300                                 if (tomoyo_add_to_gc(TOMOYO_ID_NAME, ptr))
 301                                         list_del_rcu(&ptr->list);
 302                                 else {
 303                                         i = TOMOYO_MAX_HASH;
 304                                         break;
 305                                 }
 306                         }
 307                 }
 308         }
 309         {
 310                 struct tomoyo_path_group *group;
 311                 list_for_each_entry_rcu(group, &tomoyo_path_group_list, list) {
 312                         struct tomoyo_path_group_member *member;
 313                         list_for_each_entry_rcu(member, &group->member_list,
 314                                                 list) {
 315                                 if (!member->is_deleted)
 316                                         continue;
 317                                 if (tomoyo_add_to_gc(TOMOYO_ID_PATH_GROUP_MEMBER,
 318                                                      member))
 319                                         list_del_rcu(&member->list);
 320                                 else
 321                                         break;
 322                         }
 323                         if (!list_empty(&group->member_list) ||
 324                             atomic_read(&group->users))
 325                                 continue;
 326                         if (tomoyo_add_to_gc(TOMOYO_ID_PATH_GROUP, group))
 327                                 list_del_rcu(&group->list);
 328                         else
 329                                 break;
 330                 }
 331         }
 332         mutex_unlock(&tomoyo_policy_lock);
 333 }
 334
 335 static void tomoyo_kfree_entry(void)
 336 {
 337         struct tomoyo_gc_entry *p;
 338         struct tomoyo_gc_entry *tmp;
 339
 340         list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) {
 341                 switch (p->type) {
 342                 case TOMOYO_ID_DOMAIN_INITIALIZER:
 343                         tomoyo_del_domain_initializer(p->element);
 344                         break;
 345                 case TOMOYO_ID_DOMAIN_KEEPER:
 346                         tomoyo_del_domain_keeper(p->element);
 347                         break;
 348                 case TOMOYO_ID_ALIAS:
 349                         tomoyo_del_alias(p->element);
 350                         break;
 351                 case TOMOYO_ID_GLOBALLY_READABLE:
 352                         tomoyo_del_allow_read(p->element);
 353                         break;
 354                 case TOMOYO_ID_PATTERN:
 355                         tomoyo_del_file_pattern(p->element);
 356                         break;
 357                 case TOMOYO_ID_NO_REWRITE:
 358                         tomoyo_del_no_rewrite(p->element);
 359                         break;
 360                 case TOMOYO_ID_MANAGER:
 361                         tomoyo_del_manager(p->element);
 362                         break;
 363                 case TOMOYO_ID_NAME:
 364                         tomoyo_del_name(p->element);
 365                         break;
 366                 case TOMOYO_ID_ACL:
 367                         tomoyo_del_acl(p->element);
 368                         break;
 369                 case TOMOYO_ID_DOMAIN:
 370                         if (!tomoyo_del_domain(p->element))
 371                                 continue;
 372                         break;
 373                 case TOMOYO_ID_PATH_GROUP_MEMBER:
 374                         tomoyo_del_path_group_member(p->element);
 375                         break;
 376                 case TOMOYO_ID_PATH_GROUP:
 377                         tomoyo_del_path_group(p->element);
 378                         break;
 379                 default:
 380                         printk(KERN_WARNING "Unknown type\n");
 381                         break;
 382                 }
 383                 tomoyo_memory_free(p->element);
 384                 list_del(&p->list);
 385                 kfree(p);
 386         }
 387 }
 388
 389 static int tomoyo_gc_thread(void *unused)
 390 {
 391         daemonize("GC for TOMOYO");
 392         if (mutex_trylock(&tomoyo_gc_mutex)) {
 393                 int i;
 394                 for (i = 0; i < 10; i++) {
 395                         tomoyo_collect_entry();
 396                         if (list_empty(&tomoyo_gc_queue))
 397                                 break;
 398                         synchronize_srcu(&tomoyo_ss);
 399                         tomoyo_kfree_entry();
 400                 }
 401                 mutex_unlock(&tomoyo_gc_mutex);
 402         }
 403         do_exit(0);
 404 }
 405
 406 void tomoyo_run_gc(void)
 407 {
 408         struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
 409                                                   "GC for TOMOYO");
 410         if (!IS_ERR(task))
 411                 wake_up_process(task);
 412 }