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   2009/04/01
   9  *
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/mount.h>
  14 #include <linux/mnt_namespace.h>
  15 #include <linux/fs_struct.h>
  16 #include <linux/hash.h>
  17
  18 #include "common.h"
  19 #include "realpath.h"
  20
  21 /**
  22  * tomoyo_encode: Convert binary string to ascii string.
  23  *
  24  * @buffer:  Buffer for ASCII string.
  25  * @buflen:  Size of @buffer.
  26  * @str:     Binary string.
  27  *
  28  * Returns 0 on success, -ENOMEM otherwise.
  29  */
  30 int tomoyo_encode(char *buffer, int buflen, const char *str)
  31 {
  32         while (1) {
  33                 const unsigned char c = *(unsigned char *) str++;
  34
  35                 if (tomoyo_is_valid(c)) {
  36                         if (--buflen <= 0)
  37                                 break;
  38                         *buffer++ = (char) c;
  39                         if (c != '\\')
  40                                 continue;
  41                         if (--buflen <= 0)
  42                                 break;
  43                         *buffer++ = (char) c;
  44                         continue;
  45                 }
  46                 if (!c) {
  47                         if (--buflen <= 0)
  48                                 break;
  49                         *buffer = '\0';
  50                         return 0;
  51                 }
  52                 buflen -= 4;
  53                 if (buflen <= 0)
  54                         break;
  55                 *buffer++ = '\\';
  56                 *buffer++ = (c >> 6) + '0';
  57                 *buffer++ = ((c >> 3) & 7) + '0';
  58                 *buffer++ = (c & 7) + '0';
  59         }
  60         return -ENOMEM;
  61 }
  62
  63 /**
  64  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
  65  *
  66  * @path:        Pointer to "struct path".
  67  * @newname:     Pointer to buffer to return value in.
  68  * @newname_len: Size of @newname.
  69  *
  70  * Returns 0 on success, negative value otherwise.
  71  *
  72  * If dentry is a directory, trailing '/' is appended.
  73  * Characters out of 0x20 < c < 0x7F range are converted to
  74  * \ooo style octal string.
  75  * Character \ is converted to \\ string.
  76  */
  77 int tomoyo_realpath_from_path2(struct path *path, char *newname,
  78                                int newname_len)
  79 {
  80         int error = -ENOMEM;
  81         struct dentry *dentry = path->dentry;
  82         char *sp;
  83
  84         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
  85                 return -EINVAL;
  86         if (dentry->d_op && dentry->d_op->d_dname) {
  87                 /* For "socket:[\$]" and "pipe:[\$]". */
  88                 static const int offset = 1536;
  89                 sp = dentry->d_op->d_dname(dentry, newname + offset,
  90                                            newname_len - offset);
  91         } else {
  92                 struct path ns_root = {.mnt = NULL, .dentry = NULL};
  93
  94                 spin_lock(&dcache_lock);
  95                 /* go to whatever namespace root we are under */
  96                 sp = __d_path(path, &ns_root, newname, newname_len);
  97                 spin_unlock(&dcache_lock);
  98                 /* Prepend "/proc" prefix if using internal proc vfs mount. */
  99                 if (!IS_ERR(sp) && (path->mnt->mnt_flags & MNT_INTERNAL) &&
 100                     (strcmp(path->mnt->mnt_sb->s_type->name, "proc") == 0)) {
 101                         sp -= 5;
 102                         if (sp >= newname)
 103                                 memcpy(sp, "/proc", 5);
 104                         else
 105                                 sp = ERR_PTR(-ENOMEM);
 106                 }
 107         }
 108         if (IS_ERR(sp))
 109                 error = PTR_ERR(sp);
 110         else
 111                 error = tomoyo_encode(newname, sp - newname, sp);
 112         /* Append trailing '/' if dentry is a directory. */
 113         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 114             && *newname) {
 115                 sp = newname + strlen(newname);
 116                 if (*(sp - 1) != '/') {
 117                         if (sp < newname + newname_len - 4) {
 118                                 *sp++ = '/';
 119                                 *sp = '\0';
 120                         } else {
 121                                 error = -ENOMEM;
 122                         }
 123                 }
 124         }
 125         if (error)
 126                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
 127         return error;
 128 }
 129
 130 /**
 131  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 132  *
 133  * @path: Pointer to "struct path".
 134  *
 135  * Returns the realpath of the given @path on success, NULL otherwise.
 136  *
 137  * These functions use tomoyo_alloc(), so the caller must call tomoyo_free()
 138  * if these functions didn't return NULL.
 139  */
 140 char *tomoyo_realpath_from_path(struct path *path)
 141 {
 142         char *buf = tomoyo_alloc(sizeof(struct tomoyo_page_buffer));
 143
 144         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 145                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 146         if (!buf)
 147                 return NULL;
 148         if (tomoyo_realpath_from_path2(path, buf,
 149                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 150                 return buf;
 151         tomoyo_free(buf);
 152         return NULL;
 153 }
 154
 155 /**
 156  * tomoyo_realpath - Get realpath of a pathname.
 157  *
 158  * @pathname: The pathname to solve.
 159  *
 160  * Returns the realpath of @pathname on success, NULL otherwise.
 161  */
 162 char *tomoyo_realpath(const char *pathname)
 163 {
 164         struct path path;
 165
 166         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
 167                 char *buf = tomoyo_realpath_from_path(&path);
 168                 path_put(&path);
 169                 return buf;
 170         }
 171         return NULL;
 172 }
 173
 174 /**
 175  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 176  *
 177  * @pathname: The pathname to solve.
 178  *
 179  * Returns the realpath of @pathname on success, NULL otherwise.
 180  */
 181 char *tomoyo_realpath_nofollow(const char *pathname)
 182 {
 183         struct path path;
 184
 185         if (pathname && kern_path(pathname, 0, &path) == 0) {
 186                 char *buf = tomoyo_realpath_from_path(&path);
 187                 path_put(&path);
 188                 return buf;
 189         }
 190         return NULL;
 191 }
 192
 193 /* Memory allocated for non-string data. */
 194 static unsigned int tomoyo_allocated_memory_for_elements;
 195 /* Quota for holding non-string data. */
 196 static unsigned int tomoyo_quota_for_elements;
 197
 198 /**
 199  * tomoyo_alloc_element - Allocate permanent memory for structures.
 200  *
 201  * @size: Size in bytes.
 202  *
 203  * Returns pointer to allocated memory on success, NULL otherwise.
 204  *
 205  * Memory has to be zeroed.
 206  * The RAM is chunked, so NEVER try to kfree() the returned pointer.
 207  */
 208 void *tomoyo_alloc_element(const unsigned int size)
 209 {
 210         static char *buf;
 211         static DEFINE_MUTEX(lock);
 212         static unsigned int buf_used_len = PATH_MAX;
 213         char *ptr = NULL;
 214         /*Assumes sizeof(void *) >= sizeof(long) is true. */
 215         const unsigned int word_aligned_size
 216                 = roundup(size, max(sizeof(void *), sizeof(long)));
 217         if (word_aligned_size > PATH_MAX)
 218                 return NULL;
 219         mutex_lock(&lock);
 220         if (buf_used_len + word_aligned_size > PATH_MAX) {
 221                 if (!tomoyo_quota_for_elements ||
 222                     tomoyo_allocated_memory_for_elements
 223                     + PATH_MAX <= tomoyo_quota_for_elements)
 224                         ptr = kzalloc(PATH_MAX, GFP_KERNEL);
 225                 if (!ptr) {
 226                         printk(KERN_WARNING "ERROR: Out of memory "
 227                                "for tomoyo_alloc_element().\n");
 228                         if (!tomoyo_policy_loaded)
 229                                 panic("MAC Initialization failed.\n");
 230                 } else {
 231                         buf = ptr;
 232                         tomoyo_allocated_memory_for_elements += PATH_MAX;
 233                         buf_used_len = word_aligned_size;
 234                         ptr = buf;
 235                 }
 236         } else if (word_aligned_size) {
 237                 int i;
 238                 ptr = buf + buf_used_len;
 239                 buf_used_len += word_aligned_size;
 240                 for (i = 0; i < word_aligned_size; i++) {
 241                         if (!ptr[i])
 242                                 continue;
 243                         printk(KERN_ERR "WARNING: Reserved memory was tainted! "
 244                                "The system might go wrong.\n");
 245                         ptr[i] = '\0';
 246                 }
 247         }
 248         mutex_unlock(&lock);
 249         return ptr;
 250 }
 251
 252 /* Memory allocated for string data in bytes. */
 253 static unsigned int tomoyo_allocated_memory_for_savename;
 254 /* Quota for holding string data in bytes. */
 255 static unsigned int tomoyo_quota_for_savename;
 256
 257 /*
 258  * TOMOYO uses this hash only when appending a string into the string
 259  * table. Frequency of appending strings is very low. So we don't need
 260  * large (e.g. 64k) hash size. 256 will be sufficient.
 261  */
 262 #define TOMOYO_HASH_BITS  8
 263 #define TOMOYO_MAX_HASH (1u<<TOMOYO_HASH_BITS)
 264
 265 /*
 266  * tomoyo_name_entry is a structure which is used for linking
 267  * "struct tomoyo_path_info" into tomoyo_name_list .
 268  *
 269  * Since tomoyo_name_list manages a list of strings which are shared by
 270  * multiple processes (whereas "struct tomoyo_path_info" inside
 271  * "struct tomoyo_path_info_with_data" is not shared), a reference counter will
 272  * be added to "struct tomoyo_name_entry" rather than "struct tomoyo_path_info"
 273  * when TOMOYO starts supporting garbage collector.
 274  */
 275 struct tomoyo_name_entry {
 276         struct list_head list;
 277         struct tomoyo_path_info entry;
 278 };
 279
 280 /* Structure for available memory region. */
 281 struct tomoyo_free_memory_block_list {
 282         struct list_head list;
 283         char *ptr;             /* Pointer to a free area. */
 284         int len;               /* Length of the area.     */
 285 };
 286
 287 /*
 288  * tomoyo_name_list is used for holding string data used by TOMOYO.
 289  * Since same string data is likely used for multiple times (e.g.
 290  * "/lib/libc-2.5.so"), TOMOYO shares string data in the form of
 291  * "const struct tomoyo_path_info *".
 292  */
 293 static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 294
 295 /**
 296  * tomoyo_save_name - Allocate permanent memory for string data.
 297  *
 298  * @name: The string to store into the permernent memory.
 299  *
 300  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 301  *
 302  * The RAM is shared, so NEVER try to modify or kfree() the returned name.
 303  */
 304 const struct tomoyo_path_info *tomoyo_save_name(const char *name)
 305 {
 306         static LIST_HEAD(fmb_list);
 307         static DEFINE_MUTEX(lock);
 308         struct tomoyo_name_entry *ptr;
 309         unsigned int hash;
 310         /* fmb contains available size in bytes.
 311            fmb is removed from the fmb_list when fmb->len becomes 0. */
 312         struct tomoyo_free_memory_block_list *fmb;
 313         int len;
 314         char *cp;
 315         struct list_head *head;
 316
 317         if (!name)
 318                 return NULL;
 319         len = strlen(name) + 1;
 320         if (len > TOMOYO_MAX_PATHNAME_LEN) {
 321                 printk(KERN_WARNING "ERROR: Name too long "
 322                        "for tomoyo_save_name().\n");
 323                 return NULL;
 324         }
 325         hash = full_name_hash((const unsigned char *) name, len - 1);
 326         head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)];
 327
 328         mutex_lock(&lock);
 329         list_for_each_entry(ptr, head, list) {
 330                 if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
 331                         goto out;
 332         }
 333         list_for_each_entry(fmb, &fmb_list, list) {
 334                 if (len <= fmb->len)
 335                         goto ready;
 336         }
 337         if (!tomoyo_quota_for_savename ||
 338             tomoyo_allocated_memory_for_savename + PATH_MAX
 339             <= tomoyo_quota_for_savename)
 340                 cp = kzalloc(PATH_MAX, GFP_KERNEL);
 341         else
 342                 cp = NULL;
 343         fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
 344         if (!cp || !fmb) {
 345                 kfree(cp);
 346                 kfree(fmb);
 347                 printk(KERN_WARNING "ERROR: Out of memory "
 348                        "for tomoyo_save_name().\n");
 349                 if (!tomoyo_policy_loaded)
 350                         panic("MAC Initialization failed.\n");
 351                 ptr = NULL;
 352                 goto out;
 353         }
 354         tomoyo_allocated_memory_for_savename += PATH_MAX;
 355         list_add(&fmb->list, &fmb_list);
 356         fmb->ptr = cp;
 357         fmb->len = PATH_MAX;
 358  ready:
 359         ptr = tomoyo_alloc_element(sizeof(*ptr));
 360         if (!ptr)
 361                 goto out;
 362         ptr->entry.name = fmb->ptr;
 363         memmove(fmb->ptr, name, len);
 364         tomoyo_fill_path_info(&ptr->entry);
 365         fmb->ptr += len;
 366         fmb->len -= len;
 367         list_add_tail(&ptr->list, head);
 368         if (fmb->len == 0) {
 369                 list_del(&fmb->list);
 370                 kfree(fmb);
 371         }
 372  out:
 373         mutex_unlock(&lock);
 374         return ptr ? &ptr->entry : NULL;
 375 }
 376
 377 /**
 378  * tomoyo_realpath_init - Initialize realpath related code.
 379  */
 380 void __init tomoyo_realpath_init(void)
 381 {
 382         int i;
 383
 384         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 385         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 386                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 387         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 388         tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
 389         list_add_tail(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 390         down_read(&tomoyo_domain_list_lock);
 391         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 392                 panic("Can't register tomoyo_kernel_domain");
 393         up_read(&tomoyo_domain_list_lock);
 394 }
 395
 396 /* Memory allocated for temporary purpose. */
 397 static atomic_t tomoyo_dynamic_memory_size;
 398
 399 /**
 400  * tomoyo_alloc - Allocate memory for temporary purpose.
 401  *
 402  * @size: Size in bytes.
 403  *
 404  * Returns pointer to allocated memory on success, NULL otherwise.
 405  */
 406 void *tomoyo_alloc(const size_t size)
 407 {
 408         void *p = kzalloc(size, GFP_KERNEL);
 409         if (p)
 410                 atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
 411         return p;
 412 }
 413
 414 /**
 415  * tomoyo_free - Release memory allocated by tomoyo_alloc().
 416  *
 417  * @p: Pointer returned by tomoyo_alloc(). May be NULL.
 418  *
 419  * Returns nothing.
 420  */
 421 void tomoyo_free(const void *p)
 422 {
 423         if (p) {
 424                 atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
 425                 kfree(p);
 426         }
 427 }
 428
 429 /**
 430  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 431  *
 432  * @head: Pointer to "struct tomoyo_io_buffer".
 433  *
 434  * Returns memory usage.
 435  */
 436 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 437 {
 438         if (!head->read_eof) {
 439                 const unsigned int shared
 440                         = tomoyo_allocated_memory_for_savename;
 441                 const unsigned int private
 442                         = tomoyo_allocated_memory_for_elements;
 443                 const unsigned int dynamic
 444                         = atomic_read(&tomoyo_dynamic_memory_size);
 445                 char buffer[64];
 446
 447                 memset(buffer, 0, sizeof(buffer));
 448                 if (tomoyo_quota_for_savename)
 449                         snprintf(buffer, sizeof(buffer) - 1,
 450                                  "   (Quota: %10u)",
 451                                  tomoyo_quota_for_savename);
 452                 else
 453                         buffer[0] = '\0';
 454                 tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
 455                 if (tomoyo_quota_for_elements)
 456                         snprintf(buffer, sizeof(buffer) - 1,
 457                                  "   (Quota: %10u)",
 458                                  tomoyo_quota_for_elements);
 459                 else
 460                         buffer[0] = '\0';
 461                 tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
 462                 tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
 463                 tomoyo_io_printf(head, "Total:   %10u\n",
 464                                  shared + private + dynamic);
 465                 head->read_eof = true;
 466         }
 467         return 0;
 468 }
 469
 470 /**
 471  * tomoyo_write_memory_quota - Set memory quota.
 472  *
 473  * @head: Pointer to "struct tomoyo_io_buffer".
 474  *
 475  * Returns 0.
 476  */
 477 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 478 {
 479         char *data = head->write_buf;
 480         unsigned int size;
 481
 482         if (sscanf(data, "Shared: %u", &size) == 1)
 483                 tomoyo_quota_for_savename = size;
 484         else if (sscanf(data, "Private: %u", &size) == 1)
 485                 tomoyo_quota_for_elements = size;
 486         return 0;
 487 }