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