security/tomoyo/realpath.c

   1 /*
   2  * security/tomoyo/realpath.c
   3  *
   4  * Get the canonicalized absolute pathnames. The basis for TOMOYO.
   5  *
   6  * Copyright (C) 2005-2009  NTT DATA CORPORATION
   7  *
   8  * Version: 2.2.0-pre   2009/02/01
   9  *
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/mount.h>
  14 #include <linux/mnt_namespace.h>
  15 #include "common.h"
  16 #include "realpath.h"
  17
  18 /**
  19  * tomoyo_encode: Convert binary string to ascii string.
  20  *
  21  * @buffer:  Buffer for ASCII string.
  22  * @buflen:  Size of @buffer.
  23  * @str:     Binary string.
  24  *
  25  * Returns 0 on success, -ENOMEM otherwise.
  26  */
  27 int tomoyo_encode(char *buffer, int buflen, const char *str)
  28 {
  29         while (1) {
  30                 const unsigned char c = *(unsigned char *) str++;
  31
  32                 if (tomoyo_is_valid(c)) {
  33                         if (--buflen <= 0)
  34                                 break;
  35                         *buffer++ = (char) c;
  36                         if (c != '\\')
  37                                 continue;
  38                         if (--buflen <= 0)
  39                                 break;
  40                         *buffer++ = (char) c;
  41                         continue;
  42                 }
  43                 if (!c) {
  44                         if (--buflen <= 0)
  45                                 break;
  46                         *buffer = '\0';
  47                         return 0;
  48                 }
  49                 buflen -= 4;
  50                 if (buflen <= 0)
  51                         break;
  52                 *buffer++ = '\\';
  53                 *buffer++ = (c >> 6) + '0';
  54                 *buffer++ = ((c >> 3) & 7) + '0';
  55                 *buffer++ = (c & 7) + '0';
  56         }
  57         return -ENOMEM;
  58 }
  59
  60 /**
  61  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
  62  *
  63  * @path:        Pointer to "struct path".
  64  * @newname:     Pointer to buffer to return value in.
  65  * @newname_len: Size of @newname.
  66  *
  67  * Returns 0 on success, negative value otherwise.
  68  *
  69  * If dentry is a directory, trailing '/' is appended.
  70  * Characters out of 0x20 < c < 0x7F range are converted to
  71  * \ooo style octal string.
  72  * Character \ is converted to \\ string.
  73  */
  74 int tomoyo_realpath_from_path2(struct path *path, char *newname,
  75                                int newname_len)
  76 {
  77         int error = -ENOMEM;
  78         struct dentry *dentry = path->dentry;
  79         char *sp;
  80
  81         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
  82                 return -EINVAL;
  83         if (dentry->d_op && dentry->d_op->d_dname) {
  84                 /* For "socket:[\$]" and "pipe:[\$]". */
  85                 static const int offset = 1536;
  86                 sp = dentry->d_op->d_dname(dentry, newname + offset,
  87                                            newname_len - offset);
  88         } else {
  89                 /* Taken from d_namespace_path(). */
  90                 struct path root;
  91                 struct path ns_root = { };
  92                 struct path tmp;
  93
  94                 read_lock(&current->fs->lock);
  95                 root = current->fs->root;
  96                 path_get(&root);
  97                 read_unlock(&current->fs->lock);
  98                 spin_lock(&vfsmount_lock);
  99                 if (root.mnt && root.mnt->mnt_ns)
 100                         ns_root.mnt = mntget(root.mnt->mnt_ns->root);
 101                 if (ns_root.mnt)
 102                         ns_root.dentry = dget(ns_root.mnt->mnt_root);
 103                 spin_unlock(&vfsmount_lock);
 104                 spin_lock(&dcache_lock);
 105                 tmp = ns_root;
 106                 sp = __d_path(path, &tmp, newname, newname_len);
 107                 spin_unlock(&dcache_lock);
 108                 path_put(&root);
 109                 path_put(&ns_root);
 110         }
 111         if (IS_ERR(sp))
 112                 error = PTR_ERR(sp);
 113         else
 114                 error = tomoyo_encode(newname, sp - newname, sp);
 115         /* Append trailing '/' if dentry is a directory. */
 116         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 117             && *newname) {
 118                 sp = newname + strlen(newname);
 119                 if (*(sp - 1) != '/') {
 120                         if (sp < newname + newname_len - 4) {
 121                                 *sp++ = '/';
 122                                 *sp = '\0';
 123                         } else {
 124                                 error = -ENOMEM;
 125                         }
 126                 }
 127         }
 128         if (error)
 129                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
 130         return error;
 131 }
 132
 133 /**
 134  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 135  *
 136  * @path: Pointer to "struct path".
 137  *
 138  * Returns the realpath of the given @path on success, NULL otherwise.
 139  *
 140  * These functions use tomoyo_alloc(), so the caller must call tomoyo_free()
 141  * if these functions didn't return NULL.
 142  */
 143 char *tomoyo_realpath_from_path(struct path *path)
 144 {
 145         char *buf = tomoyo_alloc(sizeof(struct tomoyo_page_buffer));
 146
 147         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 148                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 149         if (!buf)
 150                 return NULL;
 151         if (tomoyo_realpath_from_path2(path, buf,
 152                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 153                 return buf;
 154         tomoyo_free(buf);
 155         return NULL;
 156 }
 157
 158 /**
 159  * tomoyo_realpath - Get realpath of a pathname.
 160  *
 161  * @pathname: The pathname to solve.
 162  *
 163  * Returns the realpath of @pathname on success, NULL otherwise.
 164  */
 165 char *tomoyo_realpath(const char *pathname)
 166 {
 167         struct nameidata nd;
 168
 169         if (pathname && path_lookup(pathname, LOOKUP_FOLLOW, &nd) == 0) {
 170                 char *buf = tomoyo_realpath_from_path(&nd.path);
 171                 path_put(&nd.path);
 172                 return buf;
 173         }
 174         return NULL;
 175 }
 176
 177 /**
 178  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 179  *
 180  * @pathname: The pathname to solve.
 181  *
 182  * Returns the realpath of @pathname on success, NULL otherwise.
 183  */
 184 char *tomoyo_realpath_nofollow(const char *pathname)
 185 {
 186         struct nameidata nd;
 187
 188         if (pathname && path_lookup(pathname, 0, &nd) == 0) {
 189                 char *buf = tomoyo_realpath_from_path(&nd.path);
 190                 path_put(&nd.path);
 191                 return buf;
 192         }
 193         return NULL;
 194 }
 195
 196 /* Memory allocated for non-string data. */
 197 static unsigned int tomoyo_allocated_memory_for_elements;
 198 /* Quota for holding non-string data. */
 199 static unsigned int tomoyo_quota_for_elements;
 200
 201 /**
 202  * tomoyo_alloc_element - Allocate permanent memory for structures.
 203  *
 204  * @size: Size in bytes.
 205  *
 206  * Returns pointer to allocated memory on success, NULL otherwise.
 207  *
 208  * Memory has to be zeroed.
 209  * The RAM is chunked, so NEVER try to kfree() the returned pointer.
 210  */
 211 void *tomoyo_alloc_element(const unsigned int size)
 212 {
 213         static char *buf;
 214         static DEFINE_MUTEX(lock);
 215         static unsigned int buf_used_len = PATH_MAX;
 216         char *ptr = NULL;
 217         /*Assumes sizeof(void *) >= sizeof(long) is true. */
 218         const unsigned int word_aligned_size
 219                 = roundup(size, max(sizeof(void *), sizeof(long)));
 220         if (word_aligned_size > PATH_MAX)
 221                 return NULL;
 222         /***** EXCLUSIVE SECTION START *****/
 223         mutex_lock(&lock);
 224         if (buf_used_len + word_aligned_size > PATH_MAX) {
 225                 if (!tomoyo_quota_for_elements ||
 226                     tomoyo_allocated_memory_for_elements
 227                     + PATH_MAX <= tomoyo_quota_for_elements)
 228                         ptr = kzalloc(PATH_MAX, GFP_KERNEL);
 229                 if (!ptr) {
 230                         printk(KERN_WARNING "ERROR: Out of memory "
 231                                "for tomoyo_alloc_element().\n");
 232                         if (!tomoyo_policy_loaded)
 233                                 panic("MAC Initialization failed.\n");
 234                 } else {
 235                         buf = ptr;
 236                         tomoyo_allocated_memory_for_elements += PATH_MAX;
 237                         buf_used_len = word_aligned_size;
 238                         ptr = buf;
 239                 }
 240         } else if (word_aligned_size) {
 241                 int i;
 242                 ptr = buf + buf_used_len;
 243                 buf_used_len += word_aligned_size;
 244                 for (i = 0; i < word_aligned_size; i++) {
 245                         if (!ptr[i])
 246                                 continue;
 247                         printk(KERN_ERR "WARNING: Reserved memory was tainted! "
 248                                "The system might go wrong.\n");
 249                         ptr[i] = '\0';
 250                 }
 251         }
 252         mutex_unlock(&lock);
 253         /***** EXCLUSIVE SECTION END *****/
 254         return ptr;
 255 }
 256
 257 /* Memory allocated for string data in bytes. */
 258 static unsigned int tomoyo_allocated_memory_for_savename;
 259 /* Quota for holding string data in bytes. */
 260 static unsigned int tomoyo_quota_for_savename;
 261
 262 /*
 263  * TOMOYO uses this hash only when appending a string into the string
 264  * table. Frequency of appending strings is very low. So we don't need
 265  * large (e.g. 64k) hash size. 256 will be sufficient.
 266  */
 267 #define TOMOYO_MAX_HASH 256
 268
 269 /* Structure for string data. */
 270 struct tomoyo_name_entry {
 271         struct list_head list;
 272         struct tomoyo_path_info entry;
 273 };
 274
 275 /* Structure for available memory region. */
 276 struct tomoyo_free_memory_block_list {
 277         struct list_head list;
 278         char *ptr;             /* Pointer to a free area. */
 279         int len;               /* Length of the area.     */
 280 };
 281
 282 /*
 283  * The list for "struct tomoyo_name_entry".
 284  *
 285  * This list is updated only inside tomoyo_save_name(), thus
 286  * no global mutex exists.
 287  */
 288 static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 289
 290 /**
 291  * tomoyo_save_name - Allocate permanent memory for string data.
 292  *
 293  * @name: The string to store into the permernent memory.
 294  *
 295  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 296  *
 297  * The RAM is shared, so NEVER try to modify or kfree() the returned name.
 298  */
 299 const struct tomoyo_path_info *tomoyo_save_name(const char *name)
 300 {
 301         static LIST_HEAD(fmb_list);
 302         static DEFINE_MUTEX(lock);
 303         struct tomoyo_name_entry *ptr;
 304         unsigned int hash;
 305         /* fmb contains available size in bytes.
 306            fmb is removed from the fmb_list when fmb->len becomes 0. */
 307         struct tomoyo_free_memory_block_list *fmb;
 308         int len;
 309         char *cp;
 310
 311         if (!name)
 312                 return NULL;
 313         len = strlen(name) + 1;
 314         if (len > TOMOYO_MAX_PATHNAME_LEN) {
 315                 printk(KERN_WARNING "ERROR: Name too long "
 316                        "for tomoyo_save_name().\n");
 317                 return NULL;
 318         }
 319         hash = full_name_hash((const unsigned char *) name, len - 1);
 320         /***** EXCLUSIVE SECTION START *****/
 321         mutex_lock(&lock);
 322         list_for_each_entry(ptr, &tomoyo_name_list[hash % TOMOYO_MAX_HASH],
 323                              list) {
 324                 if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
 325                         goto out;
 326         }
 327         list_for_each_entry(fmb, &fmb_list, list) {
 328                 if (len <= fmb->len)
 329                         goto ready;
 330         }
 331         if (!tomoyo_quota_for_savename ||
 332             tomoyo_allocated_memory_for_savename + PATH_MAX
 333             <= tomoyo_quota_for_savename)
 334                 cp = kzalloc(PATH_MAX, GFP_KERNEL);
 335         else
 336                 cp = NULL;
 337         fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
 338         if (!cp || !fmb) {
 339                 kfree(cp);
 340                 kfree(fmb);
 341                 printk(KERN_WARNING "ERROR: Out of memory "
 342                        "for tomoyo_save_name().\n");
 343                 if (!tomoyo_policy_loaded)
 344                         panic("MAC Initialization failed.\n");
 345                 ptr = NULL;
 346                 goto out;
 347         }
 348         tomoyo_allocated_memory_for_savename += PATH_MAX;
 349         list_add(&fmb->list, &fmb_list);
 350         fmb->ptr = cp;
 351         fmb->len = PATH_MAX;
 352  ready:
 353         ptr = tomoyo_alloc_element(sizeof(*ptr));
 354         if (!ptr)
 355                 goto out;
 356         ptr->entry.name = fmb->ptr;
 357         memmove(fmb->ptr, name, len);
 358         tomoyo_fill_path_info(&ptr->entry);
 359         fmb->ptr += len;
 360         fmb->len -= len;
 361         list_add_tail(&ptr->list, &tomoyo_name_list[hash % TOMOYO_MAX_HASH]);
 362         if (fmb->len == 0) {
 363                 list_del(&fmb->list);
 364                 kfree(fmb);
 365         }
 366  out:
 367         mutex_unlock(&lock);
 368         /***** EXCLUSIVE SECTION END *****/
 369         return ptr ? &ptr->entry : NULL;
 370 }
 371
 372 /**
 373  * tomoyo_realpath_init - Initialize realpath related code.
 374  */
 375 void __init tomoyo_realpath_init(void)
 376 {
 377         int i;
 378
 379         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 380         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 381                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 382         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 383         tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
 384         list_add_tail(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 385         down_read(&tomoyo_domain_list_lock);
 386         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 387                 panic("Can't register tomoyo_kernel_domain");
 388         up_read(&tomoyo_domain_list_lock);
 389 }
 390
 391 /* Memory allocated for temporary purpose. */
 392 static atomic_t tomoyo_dynamic_memory_size;
 393
 394 /**
 395  * tomoyo_alloc - Allocate memory for temporary purpose.
 396  *
 397  * @size: Size in bytes.
 398  *
 399  * Returns pointer to allocated memory on success, NULL otherwise.
 400  */
 401 void *tomoyo_alloc(const size_t size)
 402 {
 403         void *p = kzalloc(size, GFP_KERNEL);
 404         if (p)
 405                 atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
 406         return p;
 407 }
 408
 409 /**
 410  * tomoyo_free - Release memory allocated by tomoyo_alloc().
 411  *
 412  * @p: Pointer returned by tomoyo_alloc(). May be NULL.
 413  *
 414  * Returns nothing.
 415  */
 416 void tomoyo_free(const void *p)
 417 {
 418         if (p) {
 419                 atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
 420                 kfree(p);
 421         }
 422 }
 423
 424 /**
 425  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 426  *
 427  * @head: Pointer to "struct tomoyo_io_buffer".
 428  *
 429  * Returns memory usage.
 430  */
 431 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 432 {
 433         if (!head->read_eof) {
 434                 const unsigned int shared
 435                         = tomoyo_allocated_memory_for_savename;
 436                 const unsigned int private
 437                         = tomoyo_allocated_memory_for_elements;
 438                 const unsigned int dynamic
 439                         = atomic_read(&tomoyo_dynamic_memory_size);
 440                 char buffer[64];
 441
 442                 memset(buffer, 0, sizeof(buffer));
 443                 if (tomoyo_quota_for_savename)
 444                         snprintf(buffer, sizeof(buffer) - 1,
 445                                  "   (Quota: %10u)",
 446                                  tomoyo_quota_for_savename);
 447                 else
 448                         buffer[0] = '\0';
 449                 tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
 450                 if (tomoyo_quota_for_elements)
 451                         snprintf(buffer, sizeof(buffer) - 1,
 452                                  "   (Quota: %10u)",
 453                                  tomoyo_quota_for_elements);
 454                 else
 455                         buffer[0] = '\0';
 456                 tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
 457                 tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
 458                 tomoyo_io_printf(head, "Total:   %10u\n",
 459                                  shared + private + dynamic);
 460                 head->read_eof = true;
 461         }
 462         return 0;
 463 }
 464
 465 /**
 466  * tomoyo_write_memory_quota - Set memory quota.
 467  *
 468  * @head: Pointer to "struct tomoyo_io_buffer".
 469  *
 470  * Returns 0.
 471  */
 472 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 473 {
 474         char *data = head->write_buf;
 475         unsigned int size;
 476
 477         if (sscanf(data, "Shared: %u", &size) == 1)
 478                 tomoyo_quota_for_savename = size;
 479         else if (sscanf(data, "Private: %u", &size) == 1)
 480                 tomoyo_quota_for_elements = size;
 481         return 0;
 482 }