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 struct tomoyo_gc {
  15         struct list_head list;
  16         enum tomoyo_policy_id type;
  17         struct list_head *element;
  18 };
  19 static LIST_HEAD(tomoyo_gc_queue);
  20 static DEFINE_MUTEX(tomoyo_gc_mutex);
  21
  22 /**
  23  * tomoyo_add_to_gc - Add an entry to to be deleted list.
  24  *
  25  * @type:    One of values in "enum tomoyo_policy_id".
  26  * @element: Pointer to "struct list_head".
  27  *
  28  * Returns true on success, false otherwise.
  29  *
  30  * Caller holds tomoyo_policy_lock mutex.
  31  *
  32  * Adding an entry needs kmalloc(). Thus, if we try to add thousands of
  33  * entries at once, it will take too long time. Thus, do not add more than 128
  34  * entries per a scan. But to be able to handle worst case where all entries
  35  * are in-use, we accept one more entry per a scan.
  36  *
  37  * If we use singly linked list using "struct list_head"->prev (which is
  38  * LIST_POISON2), we can avoid kmalloc().
  39  */
  40 static bool tomoyo_add_to_gc(const int type, struct list_head *element)
  41 {
  42         struct tomoyo_gc *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
  43         if (!entry)
  44                 return false;
  45         entry->type = type;
  46         entry->element = element;
  47         list_add(&entry->list, &tomoyo_gc_queue);
  48         list_del_rcu(element);
  49         return true;
  50 }
  51
  52 /**
  53  * tomoyo_del_transition_control - Delete members in "struct tomoyo_transition_control".
  54  *
  55  * @element: Pointer to "struct list_head".
  56  *
  57  * Returns nothing.
  58  */
  59 static void tomoyo_del_transition_control(struct list_head *element)
  60 {
  61         struct tomoyo_transition_control *ptr =
  62                 container_of(element, typeof(*ptr), head.list);
  63         tomoyo_put_name(ptr->domainname);
  64         tomoyo_put_name(ptr->program);
  65 }
  66
  67 /**
  68  * tomoyo_del_aggregator - Delete members in "struct tomoyo_aggregator".
  69  *
  70  * @element: Pointer to "struct list_head".
  71  *
  72  * Returns nothing.
  73  */
  74 static void tomoyo_del_aggregator(struct list_head *element)
  75 {
  76         struct tomoyo_aggregator *ptr =
  77                 container_of(element, typeof(*ptr), head.list);
  78         tomoyo_put_name(ptr->original_name);
  79         tomoyo_put_name(ptr->aggregated_name);
  80 }
  81
  82 /**
  83  * tomoyo_del_manager - Delete members in "struct tomoyo_manager".
  84  *
  85  * @element: Pointer to "struct list_head".
  86  *
  87  * Returns nothing.
  88  */
  89 static void tomoyo_del_manager(struct list_head *element)
  90 {
  91         struct tomoyo_manager *ptr =
  92                 container_of(element, typeof(*ptr), head.list);
  93         tomoyo_put_name(ptr->manager);
  94 }
  95
  96 /**
  97  * tomoyo_del_acl - Delete members in "struct tomoyo_acl_info".
  98  *
  99  * @element: Pointer to "struct list_head".
 100  *
 101  * Returns nothing.
 102  */
 103 static void tomoyo_del_acl(struct list_head *element)
 104 {
 105         struct tomoyo_acl_info *acl =
 106                 container_of(element, typeof(*acl), list);
 107         switch (acl->type) {
 108         case TOMOYO_TYPE_PATH_ACL:
 109                 {
 110                         struct tomoyo_path_acl *entry
 111                                 = container_of(acl, typeof(*entry), head);
 112                         tomoyo_put_name_union(&entry->name);
 113                 }
 114                 break;
 115         case TOMOYO_TYPE_PATH2_ACL:
 116                 {
 117                         struct tomoyo_path2_acl *entry
 118                                 = container_of(acl, typeof(*entry), head);
 119                         tomoyo_put_name_union(&entry->name1);
 120                         tomoyo_put_name_union(&entry->name2);
 121                 }
 122                 break;
 123         case TOMOYO_TYPE_PATH_NUMBER_ACL:
 124                 {
 125                         struct tomoyo_path_number_acl *entry
 126                                 = container_of(acl, typeof(*entry), head);
 127                         tomoyo_put_name_union(&entry->name);
 128                         tomoyo_put_number_union(&entry->number);
 129                 }
 130                 break;
 131         case TOMOYO_TYPE_MKDEV_ACL:
 132                 {
 133                         struct tomoyo_mkdev_acl *entry
 134                                 = container_of(acl, typeof(*entry), head);
 135                         tomoyo_put_name_union(&entry->name);
 136                         tomoyo_put_number_union(&entry->mode);
 137                         tomoyo_put_number_union(&entry->major);
 138                         tomoyo_put_number_union(&entry->minor);
 139                 }
 140                 break;
 141         case TOMOYO_TYPE_MOUNT_ACL:
 142                 {
 143                         struct tomoyo_mount_acl *entry
 144                                 = container_of(acl, typeof(*entry), head);
 145                         tomoyo_put_name_union(&entry->dev_name);
 146                         tomoyo_put_name_union(&entry->dir_name);
 147                         tomoyo_put_name_union(&entry->fs_type);
 148                         tomoyo_put_number_union(&entry->flags);
 149                 }
 150                 break;
 151         }
 152 }
 153
 154 static bool tomoyo_del_domain(struct list_head *element)
 155 {
 156         struct tomoyo_domain_info *domain =
 157                 container_of(element, typeof(*domain), list);
 158         struct tomoyo_acl_info *acl;
 159         struct tomoyo_acl_info *tmp;
 160         /*
 161          * Since we don't protect whole execve() operation using SRCU,
 162          * we need to recheck domain->users at this point.
 163          *
 164          * (1) Reader starts SRCU section upon execve().
 165          * (2) Reader traverses tomoyo_domain_list and finds this domain.
 166          * (3) Writer marks this domain as deleted.
 167          * (4) Garbage collector removes this domain from tomoyo_domain_list
 168          *     because this domain is marked as deleted and used by nobody.
 169          * (5) Reader saves reference to this domain into
 170          *     "struct linux_binprm"->cred->security .
 171          * (6) Reader finishes SRCU section, although execve() operation has
 172          *     not finished yet.
 173          * (7) Garbage collector waits for SRCU synchronization.
 174          * (8) Garbage collector kfree() this domain because this domain is
 175          *     used by nobody.
 176          * (9) Reader finishes execve() operation and restores this domain from
 177          *     "struct linux_binprm"->cred->security.
 178          *
 179          * By updating domain->users at (5), we can solve this race problem
 180          * by rechecking domain->users at (8).
 181          */
 182         if (atomic_read(&domain->users))
 183                 return false;
 184         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
 185                 tomoyo_del_acl(&acl->list);
 186                 tomoyo_memory_free(acl);
 187         }
 188         tomoyo_put_name(domain->domainname);
 189         return true;
 190 }
 191
 192
 193 /**
 194  * tomoyo_del_name - Delete members in "struct tomoyo_name".
 195  *
 196  * @element: Pointer to "struct list_head".
 197  *
 198  * Returns nothing.
 199  */
 200 static void tomoyo_del_name(struct list_head *element)
 201 {
 202         const struct tomoyo_name *ptr =
 203                 container_of(element, typeof(*ptr), head.list);
 204 }
 205
 206 /**
 207  * tomoyo_del_path_group - Delete members in "struct tomoyo_path_group".
 208  *
 209  * @element: Pointer to "struct list_head".
 210  *
 211  * Returns nothing.
 212  */
 213 static void tomoyo_del_path_group(struct list_head *element)
 214 {
 215         struct tomoyo_path_group *member =
 216                 container_of(element, typeof(*member), head.list);
 217         tomoyo_put_name(member->member_name);
 218 }
 219
 220 /**
 221  * tomoyo_del_group - Delete "struct tomoyo_group".
 222  *
 223  * @element: Pointer to "struct list_head".
 224  *
 225  * Returns nothing.
 226  */
 227 static void tomoyo_del_group(struct list_head *element)
 228 {
 229         struct tomoyo_group *group =
 230                 container_of(element, typeof(*group), head.list);
 231         tomoyo_put_name(group->group_name);
 232 }
 233
 234 /**
 235  * tomoyo_del_number_group - Delete members in "struct tomoyo_number_group".
 236  *
 237  * @element: Pointer to "struct list_head".
 238  *
 239  * Returns nothing.
 240  */
 241 static void tomoyo_del_number_group(struct list_head *element)
 242 {
 243         struct tomoyo_number_group *member =
 244                 container_of(element, typeof(*member), head.list);
 245 }
 246
 247 /**
 248  * tomoyo_collect_member - Delete elements with "struct tomoyo_acl_head".
 249  *
 250  * @id:          One of values in "enum tomoyo_policy_id".
 251  * @member_list: Pointer to "struct list_head".
 252  *
 253  * Returns true if some elements are deleted, false otherwise.
 254  */
 255 static bool tomoyo_collect_member(const enum tomoyo_policy_id id,
 256                                   struct list_head *member_list)
 257 {
 258         struct tomoyo_acl_head *member;
 259         list_for_each_entry(member, member_list, list) {
 260                 if (!member->is_deleted)
 261                         continue;
 262                 if (!tomoyo_add_to_gc(id, &member->list))
 263                         return false;
 264         }
 265         return true;
 266 }
 267
 268 static bool tomoyo_collect_acl(struct tomoyo_domain_info *domain)
 269 {
 270         struct tomoyo_acl_info *acl;
 271         list_for_each_entry(acl, &domain->acl_info_list, list) {
 272                 if (!acl->is_deleted)
 273                         continue;
 274                 if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
 275                         return false;
 276         }
 277         return true;
 278 }
 279
 280 /**
 281  * tomoyo_collect_entry - Scan lists for deleted elements.
 282  *
 283  * Returns nothing.
 284  */
 285 static void tomoyo_collect_entry(void)
 286 {
 287         int i;
 288         if (mutex_lock_interruptible(&tomoyo_policy_lock))
 289                 return;
 290         for (i = 0; i < TOMOYO_MAX_POLICY; i++) {
 291                 if (!tomoyo_collect_member(i, &tomoyo_policy_list[i]))
 292                         goto unlock;
 293         }
 294         {
 295                 struct tomoyo_domain_info *domain;
 296                 list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
 297                         if (!tomoyo_collect_acl(domain))
 298                                 goto unlock;
 299                         if (!domain->is_deleted || atomic_read(&domain->users))
 300                                 continue;
 301                         /*
 302                          * Nobody is referring this domain. But somebody may
 303                          * refer this domain after successful execve().
 304                          * We recheck domain->users after SRCU synchronization.
 305                          */
 306                         if (!tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, &domain->list))
 307                                 goto unlock;
 308                 }
 309         }
 310         for (i = 0; i < TOMOYO_MAX_HASH; i++) {
 311                 struct tomoyo_name *ptr;
 312                 list_for_each_entry_rcu(ptr, &tomoyo_name_list[i], head.list) {
 313                         if (atomic_read(&ptr->head.users))
 314                                 continue;
 315                         if (!tomoyo_add_to_gc(TOMOYO_ID_NAME, &ptr->head.list))
 316                                 goto unlock;
 317                 }
 318         }
 319         for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
 320                 struct list_head *list = &tomoyo_group_list[i];
 321                 int id;
 322                 struct tomoyo_group *group;
 323                 switch (i) {
 324                 case 0:
 325                         id = TOMOYO_ID_PATH_GROUP;
 326                         break;
 327                 default:
 328                         id = TOMOYO_ID_NUMBER_GROUP;
 329                         break;
 330                 }
 331                 list_for_each_entry(group, list, head.list) {
 332                         if (!tomoyo_collect_member(id, &group->member_list))
 333                                 goto unlock;
 334                         if (!list_empty(&group->member_list) ||
 335                             atomic_read(&group->head.users))
 336                                 continue;
 337                         if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP,
 338                                               &group->head.list))
 339                                 goto unlock;
 340                 }
 341         }
 342  unlock:
 343         mutex_unlock(&tomoyo_policy_lock);
 344 }
 345
 346 static void tomoyo_kfree_entry(void)
 347 {
 348         struct tomoyo_gc *p;
 349         struct tomoyo_gc *tmp;
 350
 351         list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) {
 352                 struct list_head *element = p->element;
 353                 switch (p->type) {
 354                 case TOMOYO_ID_TRANSITION_CONTROL:
 355                         tomoyo_del_transition_control(element);
 356                         break;
 357                 case TOMOYO_ID_AGGREGATOR:
 358                         tomoyo_del_aggregator(element);
 359                         break;
 360                 case TOMOYO_ID_MANAGER:
 361                         tomoyo_del_manager(element);
 362                         break;
 363                 case TOMOYO_ID_NAME:
 364                         tomoyo_del_name(element);
 365                         break;
 366                 case TOMOYO_ID_ACL:
 367                         tomoyo_del_acl(element);
 368                         break;
 369                 case TOMOYO_ID_DOMAIN:
 370                         if (!tomoyo_del_domain(element))
 371                                 continue;
 372                         break;
 373                 case TOMOYO_ID_PATH_GROUP:
 374                         tomoyo_del_path_group(element);
 375                         break;
 376                 case TOMOYO_ID_GROUP:
 377                         tomoyo_del_group(element);
 378                         break;
 379                 case TOMOYO_ID_NUMBER_GROUP:
 380                         tomoyo_del_number_group(element);
 381                         break;
 382                 case TOMOYO_MAX_POLICY:
 383                         break;
 384                 }
 385                 tomoyo_memory_free(element);
 386                 list_del(&p->list);
 387                 kfree(p);
 388         }
 389 }
 390
 391 /**
 392  * tomoyo_gc_thread - Garbage collector thread function.
 393  *
 394  * @unused: Unused.
 395  *
 396  * In case OOM-killer choose this thread for termination, we create this thread
 397  * as a short live thread whenever /sys/kernel/security/tomoyo/ interface was
 398  * close()d.
 399  *
 400  * Returns 0.
 401  */
 402 static int tomoyo_gc_thread(void *unused)
 403 {
 404         daemonize("GC for TOMOYO");
 405         if (mutex_trylock(&tomoyo_gc_mutex)) {
 406                 int i;
 407                 for (i = 0; i < 10; i++) {
 408                         tomoyo_collect_entry();
 409                         if (list_empty(&tomoyo_gc_queue))
 410                                 break;
 411                         synchronize_srcu(&tomoyo_ss);
 412                         tomoyo_kfree_entry();
 413                 }
 414                 mutex_unlock(&tomoyo_gc_mutex);
 415         }
 416         do_exit(0);
 417 }
 418
 419 void tomoyo_run_gc(void)
 420 {
 421         struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
 422                                                   "GC for TOMOYO");
 423         if (!IS_ERR(task))
 424                 wake_up_process(task);
 425 }