summaryrefslogtreecommitdiffstats
path: root/security/tomoyo/realpath.c
blob: 5fd48d23a2177c05658045a504503acd14ebbc0f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
/*
 * security/tomoyo/realpath.c
 *
 * Get the canonicalized absolute pathnames. The basis for TOMOYO.
 *
 * Copyright (C) 2005-2009  NTT DATA CORPORATION
 *
 * Version: 2.2.0-pre   2009/02/01
 *
 */

#include <linux/types.h>
#include <linux/mount.h>
#include <linux/mnt_namespace.h>
#include "common.h"
#include "realpath.h"

/**
 * tomoyo_encode: Convert binary string to ascii string.
 *
 * @buffer:  Buffer for ASCII string.
 * @buflen:  Size of @buffer.
 * @str:     Binary string.
 *
 * Returns 0 on success, -ENOMEM otherwise.
 */
int tomoyo_encode(char *buffer, int buflen, const char *str)
{
	while (1) {
		const unsigned char c = *(unsigned char *) str++;

		if (tomoyo_is_valid(c)) {
			if (--buflen <= 0)
				break;
			*buffer++ = (char) c;
			if (c != '\\')
				continue;
			if (--buflen <= 0)
				break;
			*buffer++ = (char) c;
			continue;
		}
		if (!c) {
			if (--buflen <= 0)
				break;
			*buffer = '\0';
			return 0;
		}
		buflen -= 4;
		if (buflen <= 0)
			break;
		*buffer++ = '\\';
		*buffer++ = (c >> 6) + '0';
		*buffer++ = ((c >> 3) & 7) + '0';
		*buffer++ = (c & 7) + '0';
	}
	return -ENOMEM;
}

/**
 * tomoyo_realpath_from_path2 - Returns realpath(3) of the given dentry but ignores chroot'ed root.
 *
 * @path:        Pointer to "struct path".
 * @newname:     Pointer to buffer to return value in.
 * @newname_len: Size of @newname.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * If dentry is a directory, trailing '/' is appended.
 * Characters out of 0x20 < c < 0x7F range are converted to
 * \ooo style octal string.
 * Character \ is converted to \\ string.
 */
int tomoyo_realpath_from_path2(struct path *path, char *newname,
			       int newname_len)
{
	int error = -ENOMEM;
	struct dentry *dentry = path->dentry;
	char *sp;

	if (!dentry || !path->mnt || !newname || newname_len <= 2048)
		return -EINVAL;
	if (dentry->d_op && dentry->d_op->d_dname) {
		/* For "socket:[\$]" and "pipe:[\$]". */
		static const int offset = 1536;
		sp = dentry->d_op->d_dname(dentry, newname + offset,
					   newname_len - offset);
	} else {
		/* Taken from d_namespace_path(). */
		struct path root;
		struct path ns_root = { };
		struct path tmp;

		read_lock(&current->fs->lock);
		root = current->fs->root;
		path_get(&root);
		read_unlock(&current->fs->lock);
		spin_lock(&vfsmount_lock);
		if (root.mnt && root.mnt->mnt_ns)
			ns_root.mnt = mntget(root.mnt->mnt_ns->root);
		if (ns_root.mnt)
			ns_root.dentry = dget(ns_root.mnt->mnt_root);
		spin_unlock(&vfsmount_lock);
		spin_lock(&dcache_lock);
		tmp = ns_root;
		sp = __d_path(path, &tmp, newname, newname_len);
		spin_unlock(&dcache_lock);
		path_put(&root);
		path_put(&ns_root);
	}
	if (IS_ERR(sp))
		error = PTR_ERR(sp);
	else
		error = tomoyo_encode(newname, sp - newname, sp);
	/* Append trailing '/' if dentry is a directory. */
	if (!error && dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)
	    && *newname) {
		sp = newname + strlen(newname);
		if (*(sp - 1) != '/') {
			if (sp < newname + newname_len - 4) {
				*sp++ = '/';
				*sp = '\0';
			} else {
				error = -ENOMEM;
			}
		}
	}
	if (error)
		printk(KERN_WARNING "tomoyo_realpath: Pathname too long.\n");
	return error;
}

/**
 * tomoyo_realpath_from_path - Returns realpath(3) of the given pathname but ignores chroot'ed root.
 *
 * @path: Pointer to "struct path".
 *
 * Returns the realpath of the given @path on success, NULL otherwise.
 *
 * These functions use tomoyo_alloc(), so the caller must call tomoyo_free()
 * if these functions didn't return NULL.
 */
char *tomoyo_realpath_from_path(struct path *path)
{
	char *buf = tomoyo_alloc(sizeof(struct tomoyo_page_buffer));

	BUILD_BUG_ON(sizeof(struct tomoyo_page_buffer)
		     <= TOMOYO_MAX_PATHNAME_LEN - 1);
	if (!buf)
		return NULL;
	if (tomoyo_realpath_from_path2(path, buf,
				       TOMOYO_MAX_PATHNAME_LEN - 1) == 0)
		return buf;
	tomoyo_free(buf);
	return NULL;
}

/**
 * tomoyo_realpath - Get realpath of a pathname.
 *
 * @pathname: The pathname to solve.
 *
 * Returns the realpath of @pathname on success, NULL otherwise.
 */
char *tomoyo_realpath(const char *pathname)
{
	struct nameidata nd;

	if (pathname && path_lookup(pathname, LOOKUP_FOLLOW, &nd) == 0) {
		char *buf = tomoyo_realpath_from_path(&nd.path);
		path_put(&nd.path);
		return buf;
	}
	return NULL;
}

/**
 * tomoyo_realpath_nofollow - Get realpath of a pathname.
 *
 * @pathname: The pathname to solve.
 *
 * Returns the realpath of @pathname on success, NULL otherwise.
 */
char *tomoyo_realpath_nofollow(const char *pathname)
{
	struct nameidata nd;

	if (pathname && path_lookup(pathname, 0, &nd) == 0) {
		char *buf = tomoyo_realpath_from_path(&nd.path);
		path_put(&nd.path);
		return buf;
	}
	return NULL;
}

/* Memory allocated for non-string data. */
static unsigned int tomoyo_allocated_memory_for_elements;
/* Quota for holding non-string data. */
static unsigned int tomoyo_quota_for_elements;

/**
 * tomoyo_alloc_element - Allocate permanent memory for structures.
 *
 * @size: Size in bytes.
 *
 * Returns pointer to allocated memory on success, NULL otherwise.
 *
 * Memory has to be zeroed.
 * The RAM is chunked, so NEVER try to kfree() the returned pointer.
 */
void *tomoyo_alloc_element(const unsigned int size)
{
	static char *buf;
	static DEFINE_MUTEX(lock);
	static unsigned int buf_used_len = PATH_MAX;
	char *ptr = NULL;
	/*Assumes sizeof(void *) >= sizeof(long) is true. */
	const unsigned int word_aligned_size
		= roundup(size, max(sizeof(void *), sizeof(long)));
	if (word_aligned_size > PATH_MAX)
		return NULL;
	/***** EXCLUSIVE SECTION START *****/
	mutex_lock(&lock);
	if (buf_used_len + word_aligned_size > PATH_MAX) {
		if (!tomoyo_quota_for_elements ||
		    tomoyo_allocated_memory_for_elements
		    + PATH_MAX <= tomoyo_quota_for_elements)
			ptr = kzalloc(PATH_MAX, GFP_KERNEL);
		if (!ptr) {
			printk(KERN_WARNING "ERROR: Out of memory "
			       "for tomoyo_alloc_element().\n");
			if (!tomoyo_policy_loaded)
				panic("MAC Initialization failed.\n");
		} else {
			buf = ptr;
			tomoyo_allocated_memory_for_elements += PATH_MAX;
			buf_used_len = word_aligned_size;
			ptr = buf;
		}
	} else if (word_aligned_size) {
		int i;
		ptr = buf + buf_used_len;
		buf_used_len += word_aligned_size;
		for (i = 0; i < word_aligned_size; i++) {
			if (!ptr[i])
				continue;
			printk(KERN_ERR "WARNING: Reserved memory was tainted! "
			       "The system might go wrong.\n");
			ptr[i] = '\0';
		}
	}
	mutex_unlock(&lock);
	/***** EXCLUSIVE SECTION END *****/
	return ptr;
}

/* Memory allocated for string data in bytes. */
static unsigned int tomoyo_allocated_memory_for_savename;
/* Quota for holding string data in bytes. */
static unsigned int tomoyo_quota_for_savename;

/*
 * TOMOYO uses this hash only when appending a string into the string
 * table. Frequency of appending strings is very low. So we don't need
 * large (e.g. 64k) hash size. 256 will be sufficient.
 */
#define TOMOYO_MAX_HASH 256

/* Structure for string data. */
struct tomoyo_name_entry {
	struct list_head list;
	struct tomoyo_path_info entry;
};

/* Structure for available memory region. */
struct tomoyo_free_memory_block_list {
	struct list_head list;
	char *ptr;             /* Pointer to a free area. */
	int len;               /* Length of the area.     */
};

/*
 * The list for "struct tomoyo_name_entry".
 *
 * This list is updated only inside tomoyo_save_name(), thus
 * no global mutex exists.
 */
static struct list_head tomoyo_name_list[TOMOYO_MAX_HASH];

/**
 * tomoyo_save_name - Allocate permanent memory for string data.
 *
 * @name: The string to store into the permernent memory.
 *
 * Returns pointer to "struct tomoyo_path_info" on success, NULL otherwise.
 *
 * The RAM is shared, so NEVER try to modify or kfree() the returned name.
 */
const struct tomoyo_path_info *tomoyo_save_name(const char *name)
{
	static LIST_HEAD(fmb_list);
	static DEFINE_MUTEX(lock);
	struct tomoyo_name_entry *ptr;
	unsigned int hash;
	/* fmb contains available size in bytes.
	   fmb is removed from the fmb_list when fmb->len becomes 0. */
	struct tomoyo_free_memory_block_list *fmb;
	int len;
	char *cp;

	if (!name)
		return NULL;
	len = strlen(name) + 1;
	if (len > TOMOYO_MAX_PATHNAME_LEN) {
		printk(KERN_WARNING "ERROR: Name too long "
		       "for tomoyo_save_name().\n");
		return NULL;
	}
	hash = full_name_hash((const unsigned char *) name, len - 1);
	/***** EXCLUSIVE SECTION START *****/
	mutex_lock(&lock);
	list_for_each_entry(ptr, &tomoyo_name_list[hash % TOMOYO_MAX_HASH],
			     list) {
		if (hash == ptr->entry.hash && !strcmp(name, ptr->entry.name))
			goto out;
	}
	list_for_each_entry(fmb, &fmb_list, list) {
		if (len <= fmb->len)
			goto ready;
	}
	if (!tomoyo_quota_for_savename ||
	    tomoyo_allocated_memory_for_savename + PATH_MAX
	    <= tomoyo_quota_for_savename)
		cp = kzalloc(PATH_MAX, GFP_KERNEL);
	else
		cp = NULL;
	fmb = kzalloc(sizeof(*fmb), GFP_KERNEL);
	if (!cp || !fmb) {
		kfree(cp);
		kfree(fmb);
		printk(KERN_WARNING "ERROR: Out of memory "
		       "for tomoyo_save_name().\n");
		if (!tomoyo_policy_loaded)
			panic("MAC Initialization failed.\n");
		ptr = NULL;
		goto out;
	}
	tomoyo_allocated_memory_for_savename += PATH_MAX;
	list_add(&fmb->list, &fmb_list);
	fmb->ptr = cp;
	fmb->len = PATH_MAX;
 ready:
	ptr = tomoyo_alloc_element(sizeof(*ptr));
	if (!ptr)
		goto out;
	ptr->entry.name = fmb->ptr;
	memmove(fmb->ptr, name, len);
	tomoyo_fill_path_info(&ptr->entry);
	fmb->ptr += len;
	fmb->len -= len;
	list_add_tail(&ptr->list, &tomoyo_name_list[hash % TOMOYO_MAX_HASH]);
	if (fmb->len == 0) {
		list_del(&fmb->list);
		kfree(fmb);
	}
 out:
	mutex_unlock(&lock);
	/***** EXCLUSIVE SECTION END *****/
	return ptr ? &ptr->entry : NULL;
}

/**
 * tomoyo_realpath_init - Initialize realpath related code.
 *
 * Returns 0.
 */
static int __init tomoyo_realpath_init(void)
{
	int i;

	BUILD_BUG_ON(TOMOYO_MAX_PATHNAME_LEN > PATH_MAX);
	for (i = 0; i < TOMOYO_MAX_HASH; i++)
		INIT_LIST_HEAD(&tomoyo_name_list[i]);
	INIT_LIST_HEAD(&tomoyo_kernel_domain.acl_info_list);
	tomoyo_kernel_domain.domainname = tomoyo_save_name(TOMOYO_ROOT_NAME);
	list_add_tail(&tomoyo_kernel_domain.list, &tomoyo_domain_list);
	down_read(&tomoyo_domain_list_lock);
	if (tomoyo_find_domain(TOMOYO_ROOT_NAME) != &tomoyo_kernel_domain)
		panic("Can't register tomoyo_kernel_domain");
	up_read(&tomoyo_domain_list_lock);
	return 0;
}

security_initcall(tomoyo_realpath_init);

/* Memory allocated for temporary purpose. */
static atomic_t tomoyo_dynamic_memory_size;

/**
 * tomoyo_alloc - Allocate memory for temporary purpose.
 *
 * @size: Size in bytes.
 *
 * Returns pointer to allocated memory on success, NULL otherwise.
 */
void *tomoyo_alloc(const size_t size)
{
	void *p = kzalloc(size, GFP_KERNEL);
	if (p)
		atomic_add(ksize(p), &tomoyo_dynamic_memory_size);
	return p;
}

/**
 * tomoyo_free - Release memory allocated by tomoyo_alloc().
 *
 * @p: Pointer returned by tomoyo_alloc(). May be NULL.
 *
 * Returns nothing.
 */
void tomoyo_free(const void *p)
{
	if (p) {
		atomic_sub(ksize(p), &tomoyo_dynamic_memory_size);
		kfree(p);
	}
}

/**
 * tomoyo_read_memory_counter - Check for memory usage in bytes.
 *
 * @head: Pointer to "struct tomoyo_io_buffer".
 *
 * Returns memory usage.
 */
int tomoyo_read_memory_counter(struct tomoyo_io_buffer *head)
{
	if (!head->read_eof) {
		const unsigned int shared
			= tomoyo_allocated_memory_for_savename;
		const unsigned int private
			= tomoyo_allocated_memory_for_elements;
		const unsigned int dynamic
			= atomic_read(&tomoyo_dynamic_memory_size);
		char buffer[64];

		memset(buffer, 0, sizeof(buffer));
		if (tomoyo_quota_for_savename)
			snprintf(buffer, sizeof(buffer) - 1,
				 "   (Quota: %10u)",
				 tomoyo_quota_for_savename);
		else
			buffer[0] = '\0';
		tomoyo_io_printf(head, "Shared:  %10u%s\n", shared, buffer);
		if (tomoyo_quota_for_elements)
			snprintf(buffer, sizeof(buffer) - 1,
				 "   (Quota: %10u)",
				 tomoyo_quota_for_elements);
		else
			buffer[0] = '\0';
		tomoyo_io_printf(head, "Private: %10u%s\n", private, buffer);
		tomoyo_io_printf(head, "Dynamic: %10u\n", dynamic);
		tomoyo_io_printf(head, "Total:   %10u\n",
				 shared + private + dynamic);
		head->read_eof = true;
	}
	return 0;
}

/**
 * tomoyo_write_memory_quota - Set memory quota.
 *
 * @head: Pointer to "struct tomoyo_io_buffer".
 *
 * Returns 0.
 */
int tomoyo_write_memory_quota(struct tomoyo_io_buffer *head)
{
	char *data = head->write_buf;
	unsigned int size;

	if (sscanf(data, "Shared: %u", &size) == 1)
		tomoyo_quota_for_savename = size;
	else if (sscanf(data, "Private: %u", &size) == 1)
		tomoyo_quota_for_elements = size;
	return 0;
}
OpenPOWER on IntegriCloud