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_memory_ok - Check memory quota.
 216  *
 217  * @ptr: Pointer to allocated memory.
 218  *
 219  * Returns true on success, false otherwise.
 220  *
 221  * Caller holds tomoyo_policy_lock.
 222  * Memory pointed by @ptr will be zeroed on success.
 223  */
 224 bool tomoyo_memory_ok(void *ptr)
 225 {
 226         int allocated_len = ptr ? ksize(ptr) : 0;
 227         bool result = false;
 228         if (!ptr || (tomoyo_quota_for_elements &&
 229                      tomoyo_allocated_memory_for_elements
 230                      + allocated_len > tomoyo_quota_for_elements)) {
 231                 printk(KERN_WARNING "ERROR: Out of memory "
 232                        "for tomoyo_alloc_element().\n");
 233                 if (!tomoyo_policy_loaded)
 234                         panic("MAC Initialization failed.\n");
 235         } else {
 236                 result = true;
 237                 tomoyo_allocated_memory_for_elements += allocated_len;
 238                 memset(ptr, 0, allocated_len);
 239         }
 240         return result;
 241 }
 242
 243 /* Memory allocated for string data in bytes. */
 244 static unsigned int tomoyo_allocated_memory_for_savename;
 245 /* Quota for holding string data in bytes. */
 246 static unsigned int tomoyo_quota_for_savename;
 247
 248 /*
 249  * TOMOYO uses this hash only when appending a string into the string
 250  * table. Frequency of appending strings is very low. So we don't need
 251  * large (e.g. 64k) hash size. 256 will be sufficient.
 252  */
 253 #define TOMOYO_HASH_BITS  8
 254 #define TOMOYO_MAX_HASH (1u<<TOMOYO_HASH_BITS)
 255
 256 /*
 257  * tomoyo_name_entry is a structure which is used for linking
 258  * "struct tomoyo_path_info" into tomoyo_name_list .
 259  *
 260  * Since tomoyo_name_list manages a list of strings which are shared by
 261  * multiple processes (whereas "struct tomoyo_path_info" inside
 262  * "struct tomoyo_path_info_with_data" is not shared), a reference counter will
 263  * be added to "struct tomoyo_name_entry" rather than "struct tomoyo_path_info"
 264  * when TOMOYO starts supporting garbage collector.
 265  */
 266 struct tomoyo_name_entry {
 267         struct list_head list;
 268         struct tomoyo_path_info entry;
 269 };
 270
 271 /*
 272  * tomoyo_name_list is used for holding string data used by TOMOYO.
 273  * Since same string data is likely used for multiple times (e.g.
 274  * "/lib/libc-2.5.so"), TOMOYO shares string data in the form of
 275  * "const struct tomoyo_path_info *".
 276  */
 277 static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 278
 279 /**
 280  * tomoyo_save_name - Allocate permanent memory for string data.
 281  *
 282  * @name: The string to store into the permernent memory.
 283  *
 284  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 285  */
 286 const struct tomoyo_path_info *tomoyo_save_name(const char *name)
 287 {
 288         static DEFINE_MUTEX(lock);
 289         struct tomoyo_name_entry *ptr;
 290         unsigned int hash;
 291         int len;
 292         int allocated_len;
 293         struct list_head *head;
 294
 295         if (!name)
 296                 return NULL;
 297         len = strlen(name) + 1;
 298         hash = full_name_hash((const unsigned char *) name, len - 1);
 299         head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)];
 300         mutex_lock(&lock);
 301         list_for_each_entry(ptr, head, list) {
 302                 if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
 303                         goto out;
 304         }
 305         ptr = kzalloc(sizeof(*ptr) + len, GFP_KERNEL);
 306         allocated_len = ptr ? ksize(ptr) : 0;
 307         if (!ptr || (tomoyo_quota_for_savename &&
 308                      tomoyo_allocated_memory_for_savename + allocated_len
 309                      > tomoyo_quota_for_savename)) {
 310                 kfree(ptr);
 311                 printk(KERN_WARNING "ERROR: Out of memory "
 312                        "for tomoyo_save_name().\n");
 313                 if (!tomoyo_policy_loaded)
 314                         panic("MAC Initialization failed.\n");
 315                 ptr = NULL;
 316                 goto out;
 317         }
 318         tomoyo_allocated_memory_for_savename += allocated_len;
 319         ptr->entry.name = ((char *) ptr) + sizeof(*ptr);
 320         memmove((char *) ptr->entry.name, name, len);
 321         tomoyo_fill_path_info(&ptr->entry);
 322         list_add_tail(&ptr->list, head);
 323  out:
 324         mutex_unlock(&lock);
 325         return ptr ? &ptr->entry : NULL;
 326 }
 327
 328 /**
 329  * tomoyo_realpath_init - Initialize realpath related code.
 330  */
 331 void __init tomoyo_realpath_init(void)
 332 {
 333         int i;
 334
 335         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 336         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 337                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 338         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 339         tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
 340         /*
 341          * tomoyo_read_lock() is not needed because this function is
 342          * called before the first "delete" request.
 343          */
 344         list_add_tail_rcu(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 345         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 346                 panic("Can't register tomoyo_kernel_domain");
 347 }
 348
 349 /* Memory allocated for temporary purpose. */
 350 static atomic_t tomoyo_dynamic_memory_size;
 351
 352 /**
 353  * tomoyo_alloc - Allocate memory for temporary purpose.
 354  *
 355  * @size: Size in bytes.
 356  *
 357  * Returns pointer to allocated memory on success, NULL otherwise.
 358  */
 359 void *tomoyo_alloc(const size_t size)
 360 {
 361         void *p = kzalloc(size, GFP_KERNEL);
 362         if (p)
 363                 atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
 364         return p;
 365 }
 366
 367 /**
 368  * tomoyo_free - Release memory allocated by tomoyo_alloc().
 369  *
 370  * @p: Pointer returned by tomoyo_alloc(). May be NULL.
 371  *
 372  * Returns nothing.
 373  */
 374 void tomoyo_free(const void *p)
 375 {
 376         if (p) {
 377                 atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
 378                 kfree(p);
 379         }
 380 }
 381
 382 /**
 383  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 384  *
 385  * @head: Pointer to "struct tomoyo_io_buffer".
 386  *
 387  * Returns memory usage.
 388  */
 389 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 390 {
 391         if (!head->read_eof) {
 392                 const unsigned int shared
 393                         = tomoyo_allocated_memory_for_savename;
 394                 const unsigned int private
 395                         = tomoyo_allocated_memory_for_elements;
 396                 const unsigned int dynamic
 397                         = atomic_read(&tomoyo_dynamic_memory_size);
 398                 char buffer[64];
 399
 400                 memset(buffer, 0, sizeof(buffer));
 401                 if (tomoyo_quota_for_savename)
 402                         snprintf(buffer, sizeof(buffer) - 1,
 403                                  "   (Quota: %10u)",
 404                                  tomoyo_quota_for_savename);
 405                 else
 406                         buffer[0] = '\0';
 407                 tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
 408                 if (tomoyo_quota_for_elements)
 409                         snprintf(buffer, sizeof(buffer) - 1,
 410                                  "   (Quota: %10u)",
 411                                  tomoyo_quota_for_elements);
 412                 else
 413                         buffer[0] = '\0';
 414                 tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
 415                 tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
 416                 tomoyo_io_printf(head, "Total:   %10u\n",
 417                                  shared + private + dynamic);
 418                 head->read_eof = true;
 419         }
 420         return 0;
 421 }
 422
 423 /**
 424  * tomoyo_write_memory_quota - Set memory quota.
 425  *
 426  * @head: Pointer to "struct tomoyo_io_buffer".
 427  *
 428  * Returns 0.
 429  */
 430 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 431 {
 432         char *data = head->write_buf;
 433         unsigned int size;
 434
 435         if (sscanf(data, "Shared: %u", &size) == 1)
 436                 tomoyo_quota_for_savename = size;
 437         else if (sscanf(data, "Private: %u", &size) == 1)
 438                 tomoyo_quota_for_elements = size;
 439         return 0;
 440 }