TOMOYO: Remove redundant markers.
[linux-3.10.git] / 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 "common.h"
17 #include "realpath.h"
18
19 /**
20  * tomoyo_encode: Convert binary string to ascii string.
21  *
22  * @buffer:  Buffer for ASCII string.
23  * @buflen:  Size of @buffer.
24  * @str:     Binary string.
25  *
26  * Returns 0 on success, -ENOMEM otherwise.
27  */
28 int tomoyo_encode(char *buffer, int buflen, const char *str)
29 {
30         while (1) {
31                 const unsigned char c = *(unsigned char *) str++;
32
33                 if (tomoyo_is_valid(c)) {
34                         if (--buflen <= 0)
35                                 break;
36                         *buffer++ = (char) c;
37                         if (c != '\\')
38                                 continue;
39                         if (--buflen <= 0)
40                                 break;
41                         *buffer++ = (char) c;
42                         continue;
43                 }
44                 if (!c) {
45                         if (--buflen <= 0)
46                                 break;
47                         *buffer = '\0';
48                         return 0;
49                 }
50                 buflen -= 4;
51                 if (buflen <= 0)
52                         break;
53                 *buffer++ = '\\';
54                 *buffer++ = (c >> 6) + '0';
55                 *buffer++ = ((c >> 3) & 7) + '0';
56                 *buffer++ = (c & 7) + '0';
57         }
58         return -ENOMEM;
59 }
60
61 /**
62  * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
63  *
64  * @path:        Pointer to "struct path".
65  * @newname:     Pointer to buffer to return value in.
66  * @newname_len: Size of @newname.
67  *
68  * Returns 0 on success, negative value otherwise.
69  *
70  * If dentry is a directory, trailing '/' is appended.
71  * Characters out of 0x20 < c < 0x7F range are converted to
72  * \ooo style octal string.
73  * Character \ is converted to \\ string.
74  */
75 int tomoyo_realpath_from_path2(struct path *path, char *newname,
76                                int newname_len)
77 {
78         int error = -ENOMEM;
79         struct dentry *dentry = path->dentry;
80         char *sp;
81
82         if (!dentry || !path->mnt || !newname || newname_len <= 2048)
83                 return -EINVAL;
84         if (dentry->d_op && dentry->d_op->d_dname) {
85                 /* For "socket:[\$]" and "pipe:[\$]". */
86                 static const int offset = 1536;
87                 sp = dentry->d_op->d_dname(dentry, newname + offset,
88                                            newname_len - offset);
89         } else {
90                 /* Taken from d_namespace_path(). */
91                 struct path root;
92                 struct path ns_root = { };
93                 struct path tmp;
94
95                 read_lock(&current->fs->lock);
96                 root = current->fs->root;
97                 path_get(&root);
98                 read_unlock(&current->fs->lock);
99                 spin_lock(&vfsmount_lock);
100                 if (root.mnt && root.mnt->mnt_ns)
101                         ns_root.mnt = mntget(root.mnt->mnt_ns->root);
102                 if (ns_root.mnt)
103                         ns_root.dentry = dget(ns_root.mnt->mnt_root);
104                 spin_unlock(&vfsmount_lock);
105                 spin_lock(&dcache_lock);
106                 tmp = ns_root;
107                 sp = __d_path(path, &tmp, newname, newname_len);
108                 spin_unlock(&dcache_lock);
109                 path_put(&root);
110                 path_put(&ns_root);
111         }
112         if (IS_ERR(sp))
113                 error = PTR_ERR(sp);
114         else
115                 error = tomoyo_encode(newname, sp - newname, sp);
116         /* Append trailing '/' if dentry is a directory. */
117         if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
118             && *newname) {
119                 sp = newname + strlen(newname);
120                 if (*(sp - 1) != '/') {
121                         if (sp < newname + newname_len - 4) {
122                                 *sp++ = '/';
123                                 *sp = '\0';
124                         } else {
125                                 error = -ENOMEM;
126                         }
127                 }
128         }
129         if (error)
130                 printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
131         return error;
132 }
133
134 /**
135  * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
136  *
137  * @path: Pointer to "struct path".
138  *
139  * Returns the realpath of the given @path on success, NULL otherwise.
140  *
141  * These functions use tomoyo_alloc(), so the caller must call tomoyo_free()
142  * if these functions didn't return NULL.
143  */
144 char *tomoyo_realpath_from_path(struct path *path)
145 {
146         char *buf = tomoyo_alloc(sizeof(struct tomoyo_page_buffer));
147
148         BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
149                      <= TOMOYO_MAX_PATHNAME_LEN - 1);
150         if (!buf)
151                 return NULL;
152         if (tomoyo_realpath_from_path2(path, buf,
153                                        TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
154                 return buf;
155         tomoyo_free(buf);
156         return NULL;
157 }
158
159 /**
160  * tomoyo_realpath - Get realpath of a pathname.
161  *
162  * @pathname: The pathname to solve.
163  *
164  * Returns the realpath of @pathname on success, NULL otherwise.
165  */
166 char *tomoyo_realpath(const char *pathname)
167 {
168         struct path path;
169
170         if (pathname && kern_path(pathname, LOOKUP_FOLLOW, &path) == 0) {
171                 char *buf = tomoyo_realpath_from_path(&path);
172                 path_put(&path);
173                 return buf;
174         }
175         return NULL;
176 }
177
178 /**
179  * tomoyo_realpath_nofollow - Get realpath of a pathname.
180  *
181  * @pathname: The pathname to solve.
182  *
183  * Returns the realpath of @pathname on success, NULL otherwise.
184  */
185 char *tomoyo_realpath_nofollow(const char *pathname)
186 {
187         struct path path;
188
189         if (pathname && kern_path(pathname, 0, &path) == 0) {
190                 char *buf = tomoyo_realpath_from_path(&path);
191                 path_put(&path);
192                 return buf;
193         }
194         return NULL;
195 }
196
197 /* Memory allocated for non-string data. */
198 static unsigned int tomoyo_allocated_memory_for_elements;
199 /* Quota for holding non-string data. */
200 static unsigned int tomoyo_quota_for_elements;
201
202 /**
203  * tomoyo_alloc_element - Allocate permanent memory for structures.
204  *
205  * @size: Size in bytes.
206  *
207  * Returns pointer to allocated memory on success, NULL otherwise.
208  *
209  * Memory has to be zeroed.
210  * The RAM is chunked, so NEVER try to kfree() the returned pointer.
211  */
212 void *tomoyo_alloc_element(const unsigned int size)
213 {
214         static char *buf;
215         static DEFINE_MUTEX(lock);
216         static unsigned int buf_used_len = PATH_MAX;
217         char *ptr = NULL;
218         /*Assumes sizeof(void *) >= sizeof(long) is true. */
219         const unsigned int word_aligned_size
220                 = roundup(size, max(sizeof(void *), sizeof(long)));
221         if (word_aligned_size > PATH_MAX)
222                 return NULL;
223         mutex_lock(&lock);
224         if (buf_used_len + word_aligned_size > PATH_MAX) {
225                 if (!tomoyo_quota_for_elements ||
226                     tomoyo_allocated_memory_for_elements
227                     + PATH_MAX <= tomoyo_quota_for_elements)
228                         ptr = kzalloc(PATH_MAX, GFP_KERNEL);
229                 if (!ptr) {
230                         printk(KERN_WARNING "ERROR: Out of memory "
231                                "for tomoyo_alloc_element().\n");
232                         if (!tomoyo_policy_loaded)
233                                 panic("MAC Initialization failed.\n");
234                 } else {
235                         buf = ptr;
236                         tomoyo_allocated_memory_for_elements += PATH_MAX;
237                         buf_used_len = word_aligned_size;
238                         ptr = buf;
239                 }
240         } else if (word_aligned_size) {
241                 int i;
242                 ptr = buf + buf_used_len;
243                 buf_used_len += word_aligned_size;
244                 for (i = 0; i < word_aligned_size; i++) {
245                         if (!ptr[i])
246                                 continue;
247                         printk(KERN_ERR "WARNING: Reserved memory was tainted! "
248                                "The system might go wrong.\n");
249                         ptr[i] = '\0';
250                 }
251         }
252         mutex_unlock(&lock);
253         return ptr;
254 }
255
256 /* Memory allocated for string data in bytes. */
257 static unsigned int tomoyo_allocated_memory_for_savename;
258 /* Quota for holding string data in bytes. */
259 static unsigned int tomoyo_quota_for_savename;
260
261 /*
262  * TOMOYO uses this hash only when appending a string into the string
263  * table. Frequency of appending strings is very low. So we don't need
264  * large (e.g. 64k) hash size. 256 will be sufficient.
265  */
266 #define TOMOYO_MAX_HASH 256
267
268 /* Structure for string data. */
269 struct tomoyo_name_entry {
270         struct list_head list;
271         struct tomoyo_path_info entry;
272 };
273
274 /* Structure for available memory region. */
275 struct tomoyo_free_memory_block_list {
276         struct list_head list;
277         char *ptr;             /* Pointer to a free area. */
278         int len;               /* Length of the area.     */
279 };
280
281 /*
282  * The list for "struct tomoyo_name_entry".
283  *
284  * This list is updated only inside tomoyo_save_name(), thus
285  * no global mutex exists.
286  */
287 static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];
288
289 /**
290  * tomoyo_save_name - Allocate permanent memory for string data.
291  *
292  * @name: The string to store into the permernent memory.
293  *
294  * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
295  *
296  * The RAM is shared, so NEVER try to modify or kfree() the returned name.
297  */
298 const struct tomoyo_path_info *tomoyo_save_name(const char *name)
299 {
300         static LIST_HEAD(fmb_list);
301         static DEFINE_MUTEX(lock);
302         struct tomoyo_name_entry *ptr;
303         unsigned int hash;
304         /* fmb contains available size in bytes.
305            fmb is removed from the fmb_list when fmb->len becomes 0. */
306         struct tomoyo_free_memory_block_list *fmb;
307         int len;
308         char *cp;
309
310         if (!name)
311                 return NULL;
312         len = strlen(name) + 1;
313         if (len > TOMOYO_MAX_PATHNAME_LEN) {
314                 printk(KERN_WARNING "ERROR: Name too long "
315                        "for tomoyo_save_name().\n");
316                 return NULL;
317         }
318         hash = full_name_hash((const unsigned char *) name, len - 1);
319         mutex_lock(&lock);
320         list_for_each_entry(ptr, &tomoyo_name_list[hash % TOMOYO_MAX_HASH],
321                              list) {
322                 if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
323                         goto out;
324         }
325         list_for_each_entry(fmb, &fmb_list, list) {
326                 if (len <= fmb->len)
327                         goto ready;
328         }
329         if (!tomoyo_quota_for_savename ||
330             tomoyo_allocated_memory_for_savename + PATH_MAX
331             <= tomoyo_quota_for_savename)
332                 cp = kzalloc(PATH_MAX, GFP_KERNEL);
333         else
334                 cp = NULL;
335         fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
336         if (!cp || !fmb) {
337                 kfree(cp);
338                 kfree(fmb);
339                 printk(KERN_WARNING "ERROR: Out of memory "
340                        "for tomoyo_save_name().\n");
341                 if (!tomoyo_policy_loaded)
342                         panic("MAC Initialization failed.\n");
343                 ptr = NULL;
344                 goto out;
345         }
346         tomoyo_allocated_memory_for_savename += PATH_MAX;
347         list_add(&fmb->list, &fmb_list);
348         fmb->ptr = cp;
349         fmb->len = PATH_MAX;
350  ready:
351         ptr = tomoyo_alloc_element(sizeof(*ptr));
352         if (!ptr)
353                 goto out;
354         ptr->entry.name = fmb->ptr;
355         memmove(fmb->ptr, name, len);
356         tomoyo_fill_path_info(&ptr->entry);
357         fmb->ptr += len;
358         fmb->len -= len;
359         list_add_tail(&ptr->list, &tomoyo_name_list[hash % TOMOYO_MAX_HASH]);
360         if (fmb->len == 0) {
361                 list_del(&fmb->list);
362                 kfree(fmb);
363         }
364  out:
365         mutex_unlock(&lock);
366         return ptr ? &ptr->entry : NULL;
367 }
368
369 /**
370  * tomoyo_realpath_init - Initialize realpath related code.
371  */
372 void __init tomoyo_realpath_init(void)
373 {
374         int i;
375
376         BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
377         for (i = 0; i < TOMOYO_MAX_HASH; i++)
378                 INIT_LIST_HEAD(&tomoyo_name_list[i]);
379         INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
380         tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
381         list_add_tail(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
382         down_read(&tomoyo_domain_list_lock);
383         if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
384                 panic("Can't register tomoyo_kernel_domain");
385         up_read(&tomoyo_domain_list_lock);
386 }
387
388 /* Memory allocated for temporary purpose. */
389 static atomic_t tomoyo_dynamic_memory_size;
390
391 /**
392  * tomoyo_alloc - Allocate memory for temporary purpose.
393  *
394  * @size: Size in bytes.
395  *
396  * Returns pointer to allocated memory on success, NULL otherwise.
397  */
398 void *tomoyo_alloc(const size_t size)
399 {
400         void *p = kzalloc(size, GFP_KERNEL);
401         if (p)
402                 atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
403         return p;
404 }
405
406 /**
407  * tomoyo_free - Release memory allocated by tomoyo_alloc().
408  *
409  * @p: Pointer returned by tomoyo_alloc(). May be NULL.
410  *
411  * Returns nothing.
412  */
413 void tomoyo_free(const void *p)
414 {
415         if (p) {
416                 atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
417                 kfree(p);
418         }
419 }
420
421 /**
422  * tomoyo_read_memory_counter - Check for memory usage in bytes.
423  *
424  * @head: Pointer to "struct tomoyo_io_buffer".
425  *
426  * Returns memory usage.
427  */
428 int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
429 {
430         if (!head->read_eof) {
431                 const unsigned int shared
432                         = tomoyo_allocated_memory_for_savename;
433                 const unsigned int private
434                         = tomoyo_allocated_memory_for_elements;
435                 const unsigned int dynamic
436                         = atomic_read(&tomoyo_dynamic_memory_size);
437                 char buffer[64];
438
439                 memset(buffer, 0, sizeof(buffer));
440                 if (tomoyo_quota_for_savename)
441                         snprintf(buffer, sizeof(buffer) - 1,
442                                  "   (Quota: %10u)",
443                                  tomoyo_quota_for_savename);
444                 else
445                         buffer[0] = '\0';
446                 tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
447                 if (tomoyo_quota_for_elements)
448                         snprintf(buffer, sizeof(buffer) - 1,
449                                  "   (Quota: %10u)",
450                                  tomoyo_quota_for_elements);
451                 else
452                         buffer[0] = '\0';
453                 tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
454                 tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
455                 tomoyo_io_printf(head, "Total:   %10u\n",
456                                  shared + private + dynamic);
457                 head->read_eof = true;
458         }
459         return 0;
460 }
461
462 /**
463  * tomoyo_write_memory_quota - Set memory quota.
464  *
465  * @head: Pointer to "struct tomoyo_io_buffer".
466  *
467  * Returns 0.
468  */
469 int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
470 {
471         char *data = head->write_buf;
472         unsigned int size;
473
474         if (sscanf(data, "Shared: %u", &size) == 1)
475                 tomoyo_quota_for_savename = size;
476         else if (sscanf(data, "Private: %u", &size) == 1)
477                 tomoyo_quota_for_elements = size;
478         return 0;
479 }