realpath.c revision 024e1a49411a1a7363e65db48edf1b09e9ee68ad
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 */ 30int 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 */ 77int 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(¤t->fs->lock); 98 root = current->fs->root; 99 path_get(&root); 100 read_unlock(¤t->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 */ 146char *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 */ 168char *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 */ 187char *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. */ 200static unsigned int tomoyo_allocated_memory_for_elements; 201/* Quota for holding non-string data. */ 202static 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 */ 214void *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. */ 259static unsigned int tomoyo_allocated_memory_for_savename; 260/* Quota for holding string data in bytes. */ 261static 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 */ 281struct tomoyo_name_entry { 282 struct list_head list; 283 struct tomoyo_path_info entry; 284}; 285 286/* Structure for available memory region. */ 287struct 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 */ 299static 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 */ 310const 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 */ 386void __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. */ 403static 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 */ 412void *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 */ 427void 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 */ 442int 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 */ 483int 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} 494