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   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                 /* Taken from d_namespace_path(). */
  93                 struct path root;
  94                 struct path ns_root = { };
  95                 struct path tmp;
  96
  97                 read_lock(&current->fs->lock);
  98                 root = current->fs->root;
  99                 path_get(&root);
 100                 read_unlock(&current->fs->lock);
 101                 spin_lock(&vfsmount_lock);
 102                 if (root.mnt && root.mnt->mnt_ns)
 103                         ns_root.mnt = mntget(root.mnt->mnt_ns->root);
 104                 if (ns_root.mnt)
 105                         ns_root.dentry = dget(ns_root.mnt->mnt_root);
 106                 spin_unlock(&vfsmount_lock);
 107                 spin_lock(&dcache_lock);
 108                 tmp = ns_root;
 109                 sp = __d_path(path, &tmp, newname, newname_len);
 110                 spin_unlock(&dcache_lock);
 111                 path_put(&root);
 112                 path_put(&ns_root);
 113         }
 114         if (IS_ERR(sp))
 115                 error = PTR_ERR(sp);
 116         else
 117                 error = tomoyo_encode(newname, sp - newname, sp);
 118         /* Append trailing '/' if dentry is a directory. */
 119         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 120             && *newname) {
 121                 sp = newname + strlen(newname);
 122                 if (*(sp - 1) != '/') {
 123                         if (sp < newname + newname_len - 4) {
 124                                 *sp++ = '/';
 125                                 *sp = '\0';
 126                         } else {
 127                                 error = -ENOMEM;
 128                         }
 129                 }
 130         }
 131         if (error)
 132                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
 133         return error;
 134 }
 135
 136 /**
 137  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 138  *
 139  * @path: Pointer to "struct path".
 140  *
 141  * Returns the realpath of the given @path on success, NULL otherwise.
 142  *
 143  * These functions use tomoyo_alloc(), so the caller must call tomoyo_free()
 144  * if these functions didn't return NULL.
 145  */
 146 char *tomoyo_realpath_from_path(struct path *path)
 147 {
 148         char *buf = tomoyo_alloc(sizeof(struct tomoyo_page_buffer));
 149
 150         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 151                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 152         if (!buf)
 153                 return NULL;
 154         if (tomoyo_realpath_from_path2(path, buf,
 155                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 156                 return buf;
 157         tomoyo_free(buf);
 158         return NULL;
 159 }
 160
 161 /**
 162  * tomoyo_realpath - Get realpath of a pathname.
 163  *
 164  * @pathname: The pathname to solve.
 165  *
 166  * Returns the realpath of @pathname on success, NULL otherwise.
 167  */
 168 char *tomoyo_realpath(const char *pathname)
 169 {
 170         struct path path;
 171
 172         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
 173                 char *buf = tomoyo_realpath_from_path(&path);
 174                 path_put(&path);
 175                 return buf;
 176         }
 177         return NULL;
 178 }
 179
 180 /**
 181  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 182  *
 183  * @pathname: The pathname to solve.
 184  *
 185  * Returns the realpath of @pathname on success, NULL otherwise.
 186  */
 187 char *tomoyo_realpath_nofollow(const char *pathname)
 188 {
 189         struct path path;
 190
 191         if (pathname && kern_path(pathname, 0, &path) == 0) {
 192                 char *buf = tomoyo_realpath_from_path(&path);
 193                 path_put(&path);
 194                 return buf;
 195         }
 196         return NULL;
 197 }
 198
 199 /* Memory allocated for non-string data. */
 200 static unsigned int tomoyo_allocated_memory_for_elements;
 201 /* Quota for holding non-string data. */
 202 static unsigned int tomoyo_quota_for_elements;
 203
 204 /**
 205  * tomoyo_alloc_element - Allocate permanent memory for structures.
 206  *
 207  * @size: Size in bytes.
 208  *
 209  * Returns pointer to allocated memory on success, NULL otherwise.
 210  *
 211  * Memory has to be zeroed.
 212  * The RAM is chunked, so NEVER try to kfree() the returned pointer.
 213  */
 214 void *tomoyo_alloc_element(const unsigned int size)
 215 {
 216         static char *buf;
 217         static DEFINE_MUTEX(lock);
 218         static unsigned int buf_used_len = PATH_MAX;
 219         char *ptr = NULL;
 220         /*Assumes sizeof(void *) >= sizeof(long) is true. */
 221         const unsigned int word_aligned_size
 222                 = roundup(size, max(sizeof(void *), sizeof(long)));
 223         if (word_aligned_size > PATH_MAX)
 224                 return NULL;
 225         mutex_lock(&lock);
 226         if (buf_used_len + word_aligned_size > PATH_MAX) {
 227                 if (!tomoyo_quota_for_elements ||
 228                     tomoyo_allocated_memory_for_elements
 229                     + PATH_MAX <= tomoyo_quota_for_elements)
 230                         ptr = kzalloc(PATH_MAX, GFP_KERNEL);
 231                 if (!ptr) {
 232                         printk(KERN_WARNING "ERROR: Out of memory "
 233                                "for tomoyo_alloc_element().\n");
 234                         if (!tomoyo_policy_loaded)
 235                                 panic("MAC Initialization failed.\n");
 236                 } else {
 237                         buf = ptr;
 238                         tomoyo_allocated_memory_for_elements += PATH_MAX;
 239                         buf_used_len = word_aligned_size;
 240                         ptr = buf;
 241                 }
 242         } else if (word_aligned_size) {
 243                 int i;
 244                 ptr = buf + buf_used_len;
 245                 buf_used_len += word_aligned_size;
 246                 for (i = 0; i < word_aligned_size; i++) {
 247                         if (!ptr[i])
 248                                 continue;
 249                         printk(KERN_ERR "WARNING: Reserved memory was tainted! "
 250                                "The system might go wrong.\n");
 251                         ptr[i] = '\0';
 252                 }
 253         }
 254         mutex_unlock(&lock);
 255         return ptr;
 256 }
 257
 258 /* Memory allocated for string data in bytes. */
 259 static unsigned int tomoyo_allocated_memory_for_savename;
 260 /* Quota for holding string data in bytes. */
 261 static unsigned int tomoyo_quota_for_savename;
 262
 263 /*
 264  * TOMOYO uses this hash only when appending a string into the string
 265  * table. Frequency of appending strings is very low. So we don't need
 266  * large (e.g. 64k) hash size. 256 will be sufficient.
 267  */
 268 #define TOMOYO_HASH_BITS  8
 269 #define TOMOYO_MAX_HASH (1u<<TOMOYO_HASH_BITS)
 270
 271 /*
 272  * tomoyo_name_entry is a structure which is used for linking
 273  * "struct tomoyo_path_info" into tomoyo_name_list .
 274  *
 275  * Since tomoyo_name_list manages a list of strings which are shared by
 276  * multiple processes (whereas "struct tomoyo_path_info" inside
 277  * "struct tomoyo_path_info_with_data" is not shared), a reference counter will
 278  * be added to "struct tomoyo_name_entry" rather than "struct tomoyo_path_info"
 279  * when TOMOYO starts supporting garbage collector.
 280  */
 281 struct tomoyo_name_entry {
 282         struct list_head list;
 283         struct tomoyo_path_info entry;
 284 };
 285
 286 /* Structure for available memory region. */
 287 struct tomoyo_free_memory_block_list {
 288         struct list_head list;
 289         char *ptr;             /* Pointer to a free area. */
 290         int len;               /* Length of the area.     */
 291 };
 292
 293 /*
 294  * tomoyo_name_list is used for holding string data used by TOMOYO.
 295  * Since same string data is likely used for multiple times (e.g.
 296  * "/lib/libc-2.5.so"), TOMOYO shares string data in the form of
 297  * "const struct tomoyo_path_info *".
 298  */
 299 static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 300
 301 /**
 302  * tomoyo_save_name - Allocate permanent memory for string data.
 303  *
 304  * @name: The string to store into the permernent memory.
 305  *
 306  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 307  *
 308  * The RAM is shared, so NEVER try to modify or kfree() the returned name.
 309  */
 310 const struct tomoyo_path_info *tomoyo_save_name(const char *name)
 311 {
 312         static LIST_HEAD(fmb_list);
 313         static DEFINE_MUTEX(lock);
 314         struct tomoyo_name_entry *ptr;
 315         unsigned int hash;
 316         /* fmb contains available size in bytes.
 317            fmb is removed from the fmb_list when fmb->len becomes 0. */
 318         struct tomoyo_free_memory_block_list *fmb;
 319         int len;
 320         char *cp;
 321         struct list_head *head;
 322
 323         if (!name)
 324                 return NULL;
 325         len = strlen(name) + 1;
 326         if (len > TOMOYO_MAX_PATHNAME_LEN) {
 327                 printk(KERN_WARNING "ERROR: Name too long "
 328                        "for tomoyo_save_name().\n");
 329                 return NULL;
 330         }
 331         hash = full_name_hash((const unsigned char *) name, len - 1);
 332         head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)];
 333
 334         mutex_lock(&lock);
 335         list_for_each_entry(ptr, head, list) {
 336                 if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
 337                         goto out;
 338         }
 339         list_for_each_entry(fmb, &fmb_list, list) {
 340                 if (len <= fmb->len)
 341                         goto ready;
 342         }
 343         if (!tomoyo_quota_for_savename ||
 344             tomoyo_allocated_memory_for_savename + PATH_MAX
 345             <= tomoyo_quota_for_savename)
 346                 cp = kzalloc(PATH_MAX, GFP_KERNEL);
 347         else
 348                 cp = NULL;
 349         fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
 350         if (!cp || !fmb) {
 351                 kfree(cp);
 352                 kfree(fmb);
 353                 printk(KERN_WARNING "ERROR: Out of memory "
 354                        "for tomoyo_save_name().\n");
 355                 if (!tomoyo_policy_loaded)
 356                         panic("MAC Initialization failed.\n");
 357                 ptr = NULL;
 358                 goto out;
 359         }
 360         tomoyo_allocated_memory_for_savename += PATH_MAX;
 361         list_add(&fmb->list, &fmb_list);
 362         fmb->ptr = cp;
 363         fmb->len = PATH_MAX;
 364  ready:
 365         ptr = tomoyo_alloc_element(sizeof(*ptr));
 366         if (!ptr)
 367                 goto out;
 368         ptr->entry.name = fmb->ptr;
 369         memmove(fmb->ptr, name, len);
 370         tomoyo_fill_path_info(&ptr->entry);
 371         fmb->ptr += len;
 372         fmb->len -= len;
 373         list_add_tail(&ptr->list, head);
 374         if (fmb->len == 0) {
 375                 list_del(&fmb->list);
 376                 kfree(fmb);
 377         }
 378  out:
 379         mutex_unlock(&lock);
 380         return ptr ? &ptr->entry : NULL;
 381 }
 382
 383 /**
 384  * tomoyo_realpath_init - Initialize realpath related code.
 385  */
 386 void __init tomoyo_realpath_init(void)
 387 {
 388         int i;
 389
 390         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 391         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 392                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 393         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 394         tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
 395         list_add_tail(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 396         down_read(&tomoyo_domain_list_lock);
 397         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 398                 panic("Can't register tomoyo_kernel_domain");
 399         up_read(&tomoyo_domain_list_lock);
 400 }
 401
 402 /* Memory allocated for temporary purpose. */
 403 static atomic_t tomoyo_dynamic_memory_size;
 404
 405 /**
 406  * tomoyo_alloc - Allocate memory for temporary purpose.
 407  *
 408  * @size: Size in bytes.
 409  *
 410  * Returns pointer to allocated memory on success, NULL otherwise.
 411  */
 412 void *tomoyo_alloc(const size_t size)
 413 {
 414         void *p = kzalloc(size, GFP_KERNEL);
 415         if (p)
 416                 atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
 417         return p;
 418 }
 419
 420 /**
 421  * tomoyo_free - Release memory allocated by tomoyo_alloc().
 422  *
 423  * @p: Pointer returned by tomoyo_alloc(). May be NULL.
 424  *
 425  * Returns nothing.
 426  */
 427 void tomoyo_free(const void *p)
 428 {
 429         if (p) {
 430                 atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
 431                 kfree(p);
 432         }
 433 }
 434
 435 /**
 436  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 437  *
 438  * @head: Pointer to "struct tomoyo_io_buffer".
 439  *
 440  * Returns memory usage.
 441  */
 442 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 443 {
 444         if (!head->read_eof) {
 445                 const unsigned int shared
 446                         = tomoyo_allocated_memory_for_savename;
 447                 const unsigned int private
 448                         = tomoyo_allocated_memory_for_elements;
 449                 const unsigned int dynamic
 450                         = atomic_read(&tomoyo_dynamic_memory_size);
 451                 char buffer[64];
 452
 453                 memset(buffer, 0, sizeof(buffer));
 454                 if (tomoyo_quota_for_savename)
 455                         snprintf(buffer, sizeof(buffer) - 1,
 456                                  "   (Quota: %10u)",
 457                                  tomoyo_quota_for_savename);
 458                 else
 459                         buffer[0] = '\0';
 460                 tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
 461                 if (tomoyo_quota_for_elements)
 462                         snprintf(buffer, sizeof(buffer) - 1,
 463                                  "   (Quota: %10u)",
 464                                  tomoyo_quota_for_elements);
 465                 else
 466                         buffer[0] = '\0';
 467                 tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
 468                 tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
 469                 tomoyo_io_printf(head, "Total:   %10u\n",
 470                                  shared + private + dynamic);
 471                 head->read_eof = true;
 472         }
 473         return 0;
 474 }
 475
 476 /**
 477  * tomoyo_write_memory_quota - Set memory quota.
 478  *
 479  * @head: Pointer to "struct tomoyo_io_buffer".
 480  *
 481  * Returns 0.
 482  */
 483 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 484 {
 485         char *data = head->write_buf;
 486         unsigned int size;
 487
 488         if (sscanf(data, "Shared: %u", &size) == 1)
 489                 tomoyo_quota_for_savename = size;
 490         else if (sscanf(data, "Private: %u", &size) == 1)
 491                 tomoyo_quota_for_elements = size;
 492         return 0;
 493 }