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         int type;
  17         struct list_head *element;
  18 };
  19 static LIST_HEAD(tomoyo_gc_queue);
  20 static DEFINE_MUTEX(tomoyo_gc_mutex);
  21
  22 /* Caller holds tomoyo_policy_lock mutex. */
  23 static bool tomoyo_add_to_gc(const int type, struct list_head *element)
  24 {
  25         struct tomoyo_gc *entry = kzalloc(sizeof(*entry), GFP_ATOMIC);
  26         if (!entry)
  27                 return false;
  28         entry->type = type;
  29         entry->element = element;
  30         list_add(&entry->list, &tomoyo_gc_queue);
  31         list_del_rcu(element);
  32         return true;
  33 }
  34
  35 static void tomoyo_del_allow_read(struct list_head *element)
  36 {
  37         struct tomoyo_readable_file *ptr =
  38                 container_of(element, typeof(*ptr), head.list);
  39         tomoyo_put_name(ptr->filename);
  40 }
  41
  42 static void tomoyo_del_file_pattern(struct list_head *element)
  43 {
  44         struct tomoyo_no_pattern *ptr =
  45                 container_of(element, typeof(*ptr), head.list);
  46         tomoyo_put_name(ptr->pattern);
  47 }
  48
  49 static void tomoyo_del_no_rewrite(struct list_head *element)
  50 {
  51         struct tomoyo_no_rewrite *ptr =
  52                 container_of(element, typeof(*ptr), head.list);
  53         tomoyo_put_name(ptr->pattern);
  54 }
  55
  56 static void tomoyo_del_transition_control(struct list_head *element)
  57 {
  58         struct tomoyo_transition_control *ptr =
  59                 container_of(element, typeof(*ptr), head.list);
  60         tomoyo_put_name(ptr->domainname);
  61         tomoyo_put_name(ptr->program);
  62 }
  63
  64 static void tomoyo_del_aggregator(struct list_head *element)
  65 {
  66         struct tomoyo_aggregator *ptr =
  67                 container_of(element, typeof(*ptr), head.list);
  68         tomoyo_put_name(ptr->original_name);
  69         tomoyo_put_name(ptr->aggregated_name);
  70 }
  71
  72 static void tomoyo_del_manager(struct list_head *element)
  73 {
  74         struct tomoyo_manager *ptr =
  75                 container_of(element, typeof(*ptr), head.list);
  76         tomoyo_put_name(ptr->manager);
  77 }
  78
  79 static void tomoyo_del_acl(struct list_head *element)
  80 {
  81         struct tomoyo_acl_info *acl =
  82                 container_of(element, typeof(*acl), list);
  83         switch (acl->type) {
  84         case TOMOYO_TYPE_PATH_ACL:
  85                 {
  86                         struct tomoyo_path_acl *entry
  87                                 = container_of(acl, typeof(*entry), head);
  88                         tomoyo_put_name_union(&entry->name);
  89                 }
  90                 break;
  91         case TOMOYO_TYPE_PATH2_ACL:
  92                 {
  93                         struct tomoyo_path2_acl *entry
  94                                 = container_of(acl, typeof(*entry), head);
  95                         tomoyo_put_name_union(&entry->name1);
  96                         tomoyo_put_name_union(&entry->name2);
  97                 }
  98                 break;
  99         case TOMOYO_TYPE_PATH_NUMBER_ACL:
 100                 {
 101                         struct tomoyo_path_number_acl *entry
 102                                 = container_of(acl, typeof(*entry), head);
 103                         tomoyo_put_name_union(&entry->name);
 104                         tomoyo_put_number_union(&entry->number);
 105                 }
 106                 break;
 107         case TOMOYO_TYPE_MKDEV_ACL:
 108                 {
 109                         struct tomoyo_mkdev_acl *entry
 110                                 = container_of(acl, typeof(*entry), head);
 111                         tomoyo_put_name_union(&entry->name);
 112                         tomoyo_put_number_union(&entry->mode);
 113                         tomoyo_put_number_union(&entry->major);
 114                         tomoyo_put_number_union(&entry->minor);
 115                 }
 116                 break;
 117         case TOMOYO_TYPE_MOUNT_ACL:
 118                 {
 119                         struct tomoyo_mount_acl *entry
 120                                 = container_of(acl, typeof(*entry), head);
 121                         tomoyo_put_name_union(&entry->dev_name);
 122                         tomoyo_put_name_union(&entry->dir_name);
 123                         tomoyo_put_name_union(&entry->fs_type);
 124                         tomoyo_put_number_union(&entry->flags);
 125                 }
 126                 break;
 127         }
 128 }
 129
 130 static bool tomoyo_del_domain(struct list_head *element)
 131 {
 132         struct tomoyo_domain_info *domain =
 133                 container_of(element, typeof(*domain), list);
 134         struct tomoyo_acl_info *acl;
 135         struct tomoyo_acl_info *tmp;
 136         /*
 137          * Since we don't protect whole execve() operation using SRCU,
 138          * we need to recheck domain->users at this point.
 139          *
 140          * (1) Reader starts SRCU section upon execve().
 141          * (2) Reader traverses tomoyo_domain_list and finds this domain.
 142          * (3) Writer marks this domain as deleted.
 143          * (4) Garbage collector removes this domain from tomoyo_domain_list
 144          *     because this domain is marked as deleted and used by nobody.
 145          * (5) Reader saves reference to this domain into
 146          *     "struct linux_binprm"->cred->security .
 147          * (6) Reader finishes SRCU section, although execve() operation has
 148          *     not finished yet.
 149          * (7) Garbage collector waits for SRCU synchronization.
 150          * (8) Garbage collector kfree() this domain because this domain is
 151          *     used by nobody.
 152          * (9) Reader finishes execve() operation and restores this domain from
 153          *     "struct linux_binprm"->cred->security.
 154          *
 155          * By updating domain->users at (5), we can solve this race problem
 156          * by rechecking domain->users at (8).
 157          */
 158         if (atomic_read(&domain->users))
 159                 return false;
 160         list_for_each_entry_safe(acl, tmp, &domain->acl_info_list, list) {
 161                 tomoyo_del_acl(&acl->list);
 162                 tomoyo_memory_free(acl);
 163         }
 164         tomoyo_put_name(domain->domainname);
 165         return true;
 166 }
 167
 168
 169 static void tomoyo_del_name(struct list_head *element)
 170 {
 171         const struct tomoyo_name *ptr =
 172                 container_of(element, typeof(*ptr), list);
 173 }
 174
 175 static void tomoyo_del_path_group(struct list_head *element)
 176 {
 177         struct tomoyo_path_group *member =
 178                 container_of(element, typeof(*member), head.list);
 179         tomoyo_put_name(member->member_name);
 180 }
 181
 182 static void tomoyo_del_group(struct list_head *element)
 183 {
 184         struct tomoyo_group *group =
 185                 container_of(element, typeof(*group), list);
 186         tomoyo_put_name(group->group_name);
 187 }
 188
 189 static void tomoyo_del_number_group(struct list_head *element)
 190 {
 191         struct tomoyo_number_group *member =
 192                 container_of(element, typeof(*member), head.list);
 193 }
 194
 195 static bool tomoyo_collect_member(struct list_head *member_list, int id)
 196 {
 197         struct tomoyo_acl_head *member;
 198         list_for_each_entry(member, member_list, list) {
 199                 if (!member->is_deleted)
 200                         continue;
 201                 if (!tomoyo_add_to_gc(id, &member->list))
 202                         return false;
 203         }
 204         return true;
 205 }
 206
 207 static bool tomoyo_collect_acl(struct tomoyo_domain_info *domain)
 208 {
 209         struct tomoyo_acl_info *acl;
 210         list_for_each_entry(acl, &domain->acl_info_list, list) {
 211                 if (!acl->is_deleted)
 212                         continue;
 213                 if (!tomoyo_add_to_gc(TOMOYO_ID_ACL, &acl->list))
 214                         return false;
 215         }
 216         return true;
 217 }
 218
 219 static void tomoyo_collect_entry(void)
 220 {
 221         int i;
 222         if (mutex_lock_interruptible(&tomoyo_policy_lock))
 223                 return;
 224         for (i = 0; i < TOMOYO_MAX_POLICY; i++) {
 225                 if (!tomoyo_collect_member(&tomoyo_policy_list[i], i))
 226                         goto unlock;
 227         }
 228         {
 229                 struct tomoyo_domain_info *domain;
 230                 list_for_each_entry_rcu(domain, &tomoyo_domain_list, list) {
 231                         if (!tomoyo_collect_acl(domain))
 232                                 goto unlock;
 233                         if (!domain->is_deleted || atomic_read(&domain->users))
 234                                 continue;
 235                         /*
 236                          * Nobody is referring this domain. But somebody may
 237                          * refer this domain after successful execve().
 238                          * We recheck domain->users after SRCU synchronization.
 239                          */
 240                         if (!tomoyo_add_to_gc(TOMOYO_ID_DOMAIN, &domain->list))
 241                                 goto unlock;
 242                 }
 243         }
 244         for (i = 0; i < TOMOYO_MAX_HASH; i++) {
 245                 struct tomoyo_name *ptr;
 246                 list_for_each_entry_rcu(ptr, &tomoyo_name_list[i], list) {
 247                         if (atomic_read(&ptr->users))
 248                                 continue;
 249                         if (!tomoyo_add_to_gc(TOMOYO_ID_NAME, &ptr->list))
 250                                 goto unlock;
 251                 }
 252         }
 253         for (i = 0; i < TOMOYO_MAX_GROUP; i++) {
 254                 struct list_head *list = &tomoyo_group_list[i];
 255                 int id;
 256                 struct tomoyo_group *group;
 257                 switch (i) {
 258                 case 0:
 259                         id = TOMOYO_ID_PATH_GROUP;
 260                         break;
 261                 default:
 262                         id = TOMOYO_ID_NUMBER_GROUP;
 263                         break;
 264                 }
 265                 list_for_each_entry(group, list, list) {
 266                         if (!tomoyo_collect_member(&group->member_list, id))
 267                                 goto unlock;
 268                         if (!list_empty(&group->member_list) ||
 269                             atomic_read(&group->users))
 270                                 continue;
 271                         if (!tomoyo_add_to_gc(TOMOYO_ID_GROUP, &group->list))
 272                                 goto unlock;
 273                 }
 274         }
 275  unlock:
 276         mutex_unlock(&tomoyo_policy_lock);
 277 }
 278
 279 static void tomoyo_kfree_entry(void)
 280 {
 281         struct tomoyo_gc *p;
 282         struct tomoyo_gc *tmp;
 283
 284         list_for_each_entry_safe(p, tmp, &tomoyo_gc_queue, list) {
 285                 struct list_head *element = p->element;
 286                 switch (p->type) {
 287                 case TOMOYO_ID_TRANSITION_CONTROL:
 288                         tomoyo_del_transition_control(element);
 289                         break;
 290                 case TOMOYO_ID_AGGREGATOR:
 291                         tomoyo_del_aggregator(element);
 292                         break;
 293                 case TOMOYO_ID_GLOBALLY_READABLE:
 294                         tomoyo_del_allow_read(element);
 295                         break;
 296                 case TOMOYO_ID_PATTERN:
 297                         tomoyo_del_file_pattern(element);
 298                         break;
 299                 case TOMOYO_ID_NO_REWRITE:
 300                         tomoyo_del_no_rewrite(element);
 301                         break;
 302                 case TOMOYO_ID_MANAGER:
 303                         tomoyo_del_manager(element);
 304                         break;
 305                 case TOMOYO_ID_NAME:
 306                         tomoyo_del_name(element);
 307                         break;
 308                 case TOMOYO_ID_ACL:
 309                         tomoyo_del_acl(element);
 310                         break;
 311                 case TOMOYO_ID_DOMAIN:
 312                         if (!tomoyo_del_domain(element))
 313                                 continue;
 314                         break;
 315                 case TOMOYO_ID_PATH_GROUP:
 316                         tomoyo_del_path_group(element);
 317                         break;
 318                 case TOMOYO_ID_GROUP:
 319                         tomoyo_del_group(element);
 320                         break;
 321                 case TOMOYO_ID_NUMBER_GROUP:
 322                         tomoyo_del_number_group(element);
 323                         break;
 324                 }
 325                 tomoyo_memory_free(element);
 326                 list_del(&p->list);
 327                 kfree(p);
 328         }
 329 }
 330
 331 static int tomoyo_gc_thread(void *unused)
 332 {
 333         daemonize("GC for TOMOYO");
 334         if (mutex_trylock(&tomoyo_gc_mutex)) {
 335                 int i;
 336                 for (i = 0; i < 10; i++) {
 337                         tomoyo_collect_entry();
 338                         if (list_empty(&tomoyo_gc_queue))
 339                                 break;
 340                         synchronize_srcu(&tomoyo_ss);
 341                         tomoyo_kfree_entry();
 342                 }
 343                 mutex_unlock(&tomoyo_gc_mutex);
 344         }
 345         do_exit(0);
 346 }
 347
 348 void tomoyo_run_gc(void)
 349 {
 350         struct task_struct *task = kthread_create(tomoyo_gc_thread, NULL,
 351                                                   "GC for TOMOYO");
 352         if (!IS_ERR(task))
 353                 wake_up_process(task);
 354 }