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 #include "common.h"
  19
  20 /**
  21  * tomoyo_encode: Convert binary string to ascii string.
  22  *
  23  * @buffer:  Buffer for ASCII string.
  24  * @buflen:  Size of @buffer.
  25  * @str:     Binary string.
  26  *
  27  * Returns 0 on success, -ENOMEM otherwise.
  28  */
  29 int tomoyo_encode(char *buffer, int buflen, const char *str)
  30 {
  31         while (1) {
  32                 const unsigned char c = *(unsigned char *) str++;
  33
  34                 if (tomoyo_is_valid(c)) {
  35                         if (--buflen <= 0)
  36                                 break;
  37                         *buffer++ = (char) c;
  38                         if (c != '\\')
  39                                 continue;
  40                         if (--buflen <= 0)
  41                                 break;
  42                         *buffer++ = (char) c;
  43                         continue;
  44                 }
  45                 if (!c) {
  46                         if (--buflen <= 0)
  47                                 break;
  48                         *buffer = '\0';
  49                         return 0;
  50                 }
  51                 buflen -= 4;
  52                 if (buflen <= 0)
  53                         break;
  54                 *buffer++ = '\\';
  55                 *buffer++ = (c >> 6) + '0';
  56                 *buffer++ = ((c >> 3) & 7) + '0';
  57                 *buffer++ = (c & 7) + '0';
  58         }
  59         return -ENOMEM;
  60 }
  61
  62 /**
  63  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
  64  *
  65  * @path:        Pointer to "struct path".
  66  * @newname:     Pointer to buffer to return value in.
  67  * @newname_len: Size of @newname.
  68  *
  69  * Returns 0 on success, negative value otherwise.
  70  *
  71  * If dentry is a directory, trailing '/' is appended.
  72  * Characters out of 0x20 < c < 0x7F range are converted to
  73  * \ooo style octal string.
  74  * Character \ is converted to \\ string.
  75  */
  76 int tomoyo_realpath_from_path2(struct path *path, char *newname,
  77                                int newname_len)
  78 {
  79         int error = -ENOMEM;
  80         struct dentry *dentry = path->dentry;
  81         char *sp;
  82
  83         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
  84                 return -EINVAL;
  85         if (dentry->d_op && dentry->d_op->d_dname) {
  86                 /* For "socket:[\$]" and "pipe:[\$]". */
  87                 static const int offset = 1536;
  88                 sp = dentry->d_op->d_dname(dentry, newname + offset,
  89                                            newname_len - offset);
  90         } else {
  91                 /* Taken from d_namespace_path(). */
  92                 struct path root;
  93                 struct path ns_root = { };
  94                 struct path tmp;
  95
  96                 read_lock(&current->fs->lock);
  97                 root = current->fs->root;
  98                 path_get(&root);
  99                 read_unlock(&current->fs->lock);
 100                 spin_lock(&vfsmount_lock);
 101                 if (root.mnt && root.mnt->mnt_ns)
 102                         ns_root.mnt = mntget(root.mnt->mnt_ns->root);
 103                 if (ns_root.mnt)
 104                         ns_root.dentry = dget(ns_root.mnt->mnt_root);
 105                 spin_unlock(&vfsmount_lock);
 106                 spin_lock(&dcache_lock);
 107                 tmp = ns_root;
 108                 sp = __d_path(path, &tmp, newname, newname_len);
 109                 spin_unlock(&dcache_lock);
 110                 path_put(&root);
 111                 path_put(&ns_root);
 112                 /* Prepend "/proc" prefix if using internal proc vfs mount. */
 113                 if (!IS_ERR(sp) && (path->mnt->mnt_parent == path->mnt) &&
 114                     (path->mnt->mnt_sb->s_magic == PROC_SUPER_MAGIC)) {
 115                         sp -= 5;
 116                         if (sp >= newname)
 117                                 memcpy(sp, "/proc", 5);
 118                         else
 119                                 sp = ERR_PTR(-ENOMEM);
 120                 }
 121         }
 122         if (IS_ERR(sp))
 123                 error = PTR_ERR(sp);
 124         else
 125                 error = tomoyo_encode(newname, sp - newname, sp);
 126         /* Append trailing '/' if dentry is a directory. */
 127         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
 128             && *newname) {
 129                 sp = newname + strlen(newname);
 130                 if (*(sp - 1) != '/') {
 131                         if (sp < newname + newname_len - 4) {
 132                                 *sp++ = '/';
 133                                 *sp = '\0';
 134                         } else {
 135                                 error = -ENOMEM;
 136                         }
 137                 }
 138         }
 139         if (error)
 140                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
 141         return error;
 142 }
 143
 144 /**
 145  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 146  *
 147  * @path: Pointer to "struct path".
 148  *
 149  * Returns the realpath of the given @path on success, NULL otherwise.
 150  *
 151  * These functions use kzalloc(), so the caller must call kfree()
 152  * if these functions didn't return NULL.
 153  */
 154 char *tomoyo_realpath_from_path(struct path *path)
 155 {
 156         char *buf = kzalloc(sizeof(struct tomoyo_page_buffer), GFP_KERNEL);
 157
 158         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
 159                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
 160         if (!buf)
 161                 return NULL;
 162         if (tomoyo_realpath_from_path2(path, buf,
 163                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
 164                 return buf;
 165         kfree(buf);
 166         return NULL;
 167 }
 168
 169 /**
 170  * tomoyo_realpath - Get realpath of a pathname.
 171  *
 172  * @pathname: The pathname to solve.
 173  *
 174  * Returns the realpath of @pathname on success, NULL otherwise.
 175  */
 176 char *tomoyo_realpath(const char *pathname)
 177 {
 178         struct path path;
 179
 180         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
 181                 char *buf = tomoyo_realpath_from_path(&path);
 182                 path_put(&path);
 183                 return buf;
 184         }
 185         return NULL;
 186 }
 187
 188 /**
 189  * tomoyo_realpath_nofollow - Get realpath of a pathname.
 190  *
 191  * @pathname: The pathname to solve.
 192  *
 193  * Returns the realpath of @pathname on success, NULL otherwise.
 194  */
 195 char *tomoyo_realpath_nofollow(const char *pathname)
 196 {
 197         struct path path;
 198
 199         if (pathname && kern_path(pathname, 0, &path) == 0) {
 200                 char *buf = tomoyo_realpath_from_path(&path);
 201                 path_put(&path);
 202                 return buf;
 203         }
 204         return NULL;
 205 }
 206
 207 /* Memory allocated for non-string data. */
 208 static atomic_t tomoyo_policy_memory_size;
 209 /* Quota for holding policy. */
 210 static unsigned int tomoyo_quota_for_policy;
 211
 212 /**
 213  * tomoyo_memory_ok - Check memory quota.
 214  *
 215  * @ptr: Pointer to allocated memory.
 216  *
 217  * Returns true on success, false otherwise.
 218  *
 219  * Caller holds tomoyo_policy_lock.
 220  * Memory pointed by @ptr will be zeroed on success.
 221  */
 222 bool tomoyo_memory_ok(void *ptr)
 223 {
 224         int allocated_len = ptr ? ksize(ptr) : 0;
 225         atomic_add(allocated_len, &tomoyo_policy_memory_size);
 226         if (ptr && (!tomoyo_quota_for_policy ||
 227                     atomic_read(&tomoyo_policy_memory_size)
 228                     <= tomoyo_quota_for_policy)) {
 229                 memset(ptr, 0, allocated_len);
 230                 return true;
 231         }
 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         return false;
 237 }
 238
 239 /**
 240  * tomoyo_memory_free - Free memory for elements.
 241  *
 242  * @ptr:  Pointer to allocated memory.
 243  */
 244 void tomoyo_memory_free(void *ptr)
 245 {
 246         atomic_sub(ksize(ptr), &tomoyo_policy_memory_size);
 247         kfree(ptr);
 248 }
 249
 250 /*
 251  * tomoyo_name_list is used for holding string data used by TOMOYO.
 252  * Since same string data is likely used for multiple times (e.g.
 253  * "/lib/libc-2.5.so"), TOMOYO shares string data in the form of
 254  * "const struct tomoyo_path_info *".
 255  */
 256 struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
 257 /* Lock for protecting tomoyo_name_list . */
 258 DEFINE_MUTEX(tomoyo_name_list_lock);
 259
 260 /**
 261  * tomoyo_get_name - Allocate permanent memory for string data.
 262  *
 263  * @name: The string to store into the permernent memory.
 264  *
 265  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 266  */
 267 const struct tomoyo_path_info *tomoyo_get_name(const char *name)
 268 {
 269         struct tomoyo_name_entry *ptr;
 270         unsigned int hash;
 271         int len;
 272         int allocated_len;
 273         struct list_head *head;
 274
 275         if (!name)
 276                 return NULL;
 277         len = strlen(name) + 1;
 278         hash = full_name_hash((const unsigned char *) name, len - 1);
 279         head = &tomoyo_name_list[hash_long(hash, TOMOYO_HASH_BITS)];
 280         mutex_lock(&tomoyo_name_list_lock);
 281         list_for_each_entry(ptr, head, list) {
 282                 if (hash != ptr->entry.hash || strcmp(name, ptr->entry.name))
 283                         continue;
 284                 atomic_inc(&ptr->users);
 285                 goto out;
 286         }
 287         ptr = kzalloc(sizeof(*ptr) + len, GFP_KERNEL);
 288         allocated_len = ptr ? ksize(ptr) : 0;
 289         if (!ptr || (tomoyo_quota_for_policy &&
 290                      atomic_read(&tomoyo_policy_memory_size) + allocated_len
 291                      > tomoyo_quota_for_policy)) {
 292                 kfree(ptr);
 293                 printk(KERN_WARNING "ERROR: Out of memory "
 294                        "for tomoyo_get_name().\n");
 295                 if (!tomoyo_policy_loaded)
 296                         panic("MAC Initialization failed.\n");
 297                 ptr = NULL;
 298                 goto out;
 299         }
 300         atomic_add(allocated_len, &tomoyo_policy_memory_size);
 301         ptr->entry.name = ((char *) ptr) + sizeof(*ptr);
 302         memmove((char *) ptr->entry.name, name, len);
 303         atomic_set(&ptr->users, 1);
 304         tomoyo_fill_path_info(&ptr->entry);
 305         list_add_tail(&ptr->list, head);
 306  out:
 307         mutex_unlock(&tomoyo_name_list_lock);
 308         return ptr ? &ptr->entry : NULL;
 309 }
 310
 311 /**
 312  * tomoyo_realpath_init - Initialize realpath related code.
 313  */
 314 void __init tomoyo_realpath_init(void)
 315 {
 316         int i;
 317
 318         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
 319         for (i = 0; i < TOMOYO_MAX_HASH; i++)
 320                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
 321         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
 322         tomoyo_kernel_domain.domainname = tomoyo_get_name(TOMOYO_ROOT_NAME);
 323         /*
 324          * tomoyo_read_lock() is not needed because this function is
 325          * called before the first "delete" request.
 326          */
 327         list_add_tail_rcu(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
 328         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
 329                 panic("Can't register tomoyo_kernel_domain");
 330 }
 331
 332 /**
 333  * tomoyo_read_memory_counter - Check for memory usage in bytes.
 334  *
 335  * @head: Pointer to "struct tomoyo_io_buffer".
 336  *
 337  * Returns memory usage.
 338  */
 339 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
 340 {
 341         if (!head->read_eof) {
 342                 const unsigned int policy
 343                         = atomic_read(&tomoyo_policy_memory_size);
 344                 char buffer[64];
 345
 346                 memset(buffer, 0, sizeof(buffer));
 347                 if (tomoyo_quota_for_policy)
 348                         snprintf(buffer, sizeof(buffer) - 1,
 349                                  "   (Quota: %10u)",
 350                                  tomoyo_quota_for_policy);
 351                 else
 352                         buffer[0] = '\0';
 353                 tomoyo_io_printf(head, "Policy:  %10u%s\n", policy, buffer);
 354                 tomoyo_io_printf(head, "Total:   %10u\n", policy);
 355                 head->read_eof = true;
 356         }
 357         return 0;
 358 }
 359
 360 /**
 361  * tomoyo_write_memory_quota - Set memory quota.
 362  *
 363  * @head: Pointer to "struct tomoyo_io_buffer".
 364  *
 365  * Returns 0.
 366  */
 367 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
 368 {
 369         char *data = head->write_buf;
 370         unsigned int size;
 371
 372         if (sscanf(data, "Policy: %u", &size) == 1)
 373                 tomoyo_quota_for_policy = size;
 374         return 0;
 375 }