1 /*
2  * index.c - NTFS kernel index handling.  Part of the Linux-NTFS project.
3  *
4  * Copyright (c) 2004-2005 Anton Altaparmakov
5  *
6  * This program/include file is free software; you can redistribute it and/or
7  * modify it under the terms of the GNU General Public License as published
8  * by the Free Software Foundation; either version 2 of the License, or
9  * (at your option) any later version.
10  *
11  * This program/include file is distributed in the hope that it will be
12  * useful, but WITHOUT ANY WARRANTY; without even the implied warranty
13  * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14  * GNU General Public License for more details.
15  *
16  * You should have received a copy of the GNU General Public License
17  * along with this program (in the main directory of the Linux-NTFS
18  * distribution in the file COPYING); if not, write to the Free Software
19  * Foundation,Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
20  */
21 
22 #include <linux/slab.h>
23 
24 #include "aops.h"
25 #include "collate.h"
26 #include "debug.h"
27 #include "index.h"
28 #include "ntfs.h"
29 
30 /**
31  * ntfs_index_ctx_get - allocate and initialize a new index context
32  * @idx_ni:	ntfs index inode with which to initialize the context
33  *
34  * Allocate a new index context, initialize it with @idx_ni and return it.
35  * Return NULL if allocation failed.
36  *
37  * Locking:  Caller must hold i_mutex on the index inode.
38  */
ntfs_index_ctx_get(ntfs_inode * idx_ni)39 ntfs_index_context *ntfs_index_ctx_get(ntfs_inode *idx_ni)
40 {
41 	ntfs_index_context *ictx;
42 
43 	ictx = kmem_cache_alloc(ntfs_index_ctx_cache, GFP_NOFS);
44 	if (ictx)
45 		*ictx = (ntfs_index_context){ .idx_ni = idx_ni };
46 	return ictx;
47 }
48 
49 /**
50  * ntfs_index_ctx_put - release an index context
51  * @ictx:	index context to free
52  *
53  * Release the index context @ictx, releasing all associated resources.
54  *
55  * Locking:  Caller must hold i_mutex on the index inode.
56  */
ntfs_index_ctx_put(ntfs_index_context * ictx)57 void ntfs_index_ctx_put(ntfs_index_context *ictx)
58 {
59 	if (ictx->entry) {
60 		if (ictx->is_in_root) {
61 			if (ictx->actx)
62 				ntfs_attr_put_search_ctx(ictx->actx);
63 			if (ictx->base_ni)
64 				unmap_mft_record(ictx->base_ni);
65 		} else {
66 			struct page *page = ictx->page;
67 			if (page) {
68 				BUG_ON(!PageLocked(page));
69 				unlock_page(page);
70 				ntfs_unmap_page(page);
71 			}
72 		}
73 	}
74 	kmem_cache_free(ntfs_index_ctx_cache, ictx);
75 	return;
76 }
77 
78 /**
79  * ntfs_index_lookup - find a key in an index and return its index entry
80  * @key:	[IN] key for which to search in the index
81  * @key_len:	[IN] length of @key in bytes
82  * @ictx:	[IN/OUT] context describing the index and the returned entry
83  *
84  * Before calling ntfs_index_lookup(), @ictx must have been obtained from a
85  * call to ntfs_index_ctx_get().
86  *
87  * Look for the @key in the index specified by the index lookup context @ictx.
88  * ntfs_index_lookup() walks the contents of the index looking for the @key.
89  *
90  * If the @key is found in the index, 0 is returned and @ictx is setup to
91  * describe the index entry containing the matching @key.  @ictx->entry is the
92  * index entry and @ictx->data and @ictx->data_len are the index entry data and
93  * its length in bytes, respectively.
94  *
95  * If the @key is not found in the index, -ENOENT is returned and @ictx is
96  * setup to describe the index entry whose key collates immediately after the
97  * search @key, i.e. this is the position in the index at which an index entry
98  * with a key of @key would need to be inserted.
99  *
100  * If an error occurs return the negative error code and @ictx is left
101  * untouched.
102  *
103  * When finished with the entry and its data, call ntfs_index_ctx_put() to free
104  * the context and other associated resources.
105  *
106  * If the index entry was modified, call flush_dcache_index_entry_page()
107  * immediately after the modification and either ntfs_index_entry_mark_dirty()
108  * or ntfs_index_entry_write() before the call to ntfs_index_ctx_put() to
109  * ensure that the changes are written to disk.
110  *
111  * Locking:  - Caller must hold i_mutex on the index inode.
112  *	     - Each page cache page in the index allocation mapping must be
113  *	       locked whilst being accessed otherwise we may find a corrupt
114  *	       page due to it being under ->writepage at the moment which
115  *	       applies the mst protection fixups before writing out and then
116  *	       removes them again after the write is complete after which it
117  *	       unlocks the page.
118  */
ntfs_index_lookup(const void * key,const int key_len,ntfs_index_context * ictx)119 int ntfs_index_lookup(const void *key, const int key_len,
120 		ntfs_index_context *ictx)
121 {
122 	VCN vcn, old_vcn;
123 	ntfs_inode *idx_ni = ictx->idx_ni;
124 	ntfs_volume *vol = idx_ni->vol;
125 	struct super_block *sb = vol->sb;
126 	ntfs_inode *base_ni = idx_ni->ext.base_ntfs_ino;
127 	MFT_RECORD *m;
128 	INDEX_ROOT *ir;
129 	INDEX_ENTRY *ie;
130 	INDEX_ALLOCATION *ia;
131 	u8 *index_end, *kaddr;
132 	ntfs_attr_search_ctx *actx;
133 	struct address_space *ia_mapping;
134 	struct page *page;
135 	int rc, err = 0;
136 
137 	ntfs_debug("Entering.");
138 	BUG_ON(!NInoAttr(idx_ni));
139 	BUG_ON(idx_ni->type != AT_INDEX_ALLOCATION);
140 	BUG_ON(idx_ni->nr_extents != -1);
141 	BUG_ON(!base_ni);
142 	BUG_ON(!key);
143 	BUG_ON(key_len <= 0);
144 	if (!ntfs_is_collation_rule_supported(
145 			idx_ni->itype.index.collation_rule)) {
146 		ntfs_error(sb, "Index uses unsupported collation rule 0x%x.  "
147 				"Aborting lookup.", le32_to_cpu(
148 				idx_ni->itype.index.collation_rule));
149 		return -EOPNOTSUPP;
150 	}
151 	/* Get hold of the mft record for the index inode. */
152 	m = map_mft_record(base_ni);
153 	if (IS_ERR(m)) {
154 		ntfs_error(sb, "map_mft_record() failed with error code %ld.",
155 				-PTR_ERR(m));
156 		return PTR_ERR(m);
157 	}
158 	actx = ntfs_attr_get_search_ctx(base_ni, m);
159 	if (unlikely(!actx)) {
160 		err = -ENOMEM;
161 		goto err_out;
162 	}
163 	/* Find the index root attribute in the mft record. */
164 	err = ntfs_attr_lookup(AT_INDEX_ROOT, idx_ni->name, idx_ni->name_len,
165 			CASE_SENSITIVE, 0, NULL, 0, actx);
166 	if (unlikely(err)) {
167 		if (err == -ENOENT) {
168 			ntfs_error(sb, "Index root attribute missing in inode "
169 					"0x%lx.", idx_ni->mft_no);
170 			err = -EIO;
171 		}
172 		goto err_out;
173 	}
174 	/* Get to the index root value (it has been verified in read_inode). */
175 	ir = (INDEX_ROOT*)((u8*)actx->attr +
176 			le16_to_cpu(actx->attr->data.resident.value_offset));
177 	index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
178 	/* The first index entry. */
179 	ie = (INDEX_ENTRY*)((u8*)&ir->index +
180 			le32_to_cpu(ir->index.entries_offset));
181 	/*
182 	 * Loop until we exceed valid memory (corruption case) or until we
183 	 * reach the last entry.
184 	 */
185 	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
186 		/* Bounds checks. */
187 		if ((u8*)ie < (u8*)actx->mrec || (u8*)ie +
188 				sizeof(INDEX_ENTRY_HEADER) > index_end ||
189 				(u8*)ie + le16_to_cpu(ie->length) > index_end)
190 			goto idx_err_out;
191 		/*
192 		 * The last entry cannot contain a key.  It can however contain
193 		 * a pointer to a child node in the B+tree so we just break out.
194 		 */
195 		if (ie->flags & INDEX_ENTRY_END)
196 			break;
197 		/* Further bounds checks. */
198 		if ((u32)sizeof(INDEX_ENTRY_HEADER) +
199 				le16_to_cpu(ie->key_length) >
200 				le16_to_cpu(ie->data.vi.data_offset) ||
201 				(u32)le16_to_cpu(ie->data.vi.data_offset) +
202 				le16_to_cpu(ie->data.vi.data_length) >
203 				le16_to_cpu(ie->length))
204 			goto idx_err_out;
205 		/* If the keys match perfectly, we setup @ictx and return 0. */
206 		if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
207 				&ie->key, key_len)) {
208 ir_done:
209 			ictx->is_in_root = true;
210 			ictx->ir = ir;
211 			ictx->actx = actx;
212 			ictx->base_ni = base_ni;
213 			ictx->ia = NULL;
214 			ictx->page = NULL;
215 done:
216 			ictx->entry = ie;
217 			ictx->data = (u8*)ie +
218 					le16_to_cpu(ie->data.vi.data_offset);
219 			ictx->data_len = le16_to_cpu(ie->data.vi.data_length);
220 			ntfs_debug("Done.");
221 			return err;
222 		}
223 		/*
224 		 * Not a perfect match, need to do full blown collation so we
225 		 * know which way in the B+tree we have to go.
226 		 */
227 		rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
228 				key_len, &ie->key, le16_to_cpu(ie->key_length));
229 		/*
230 		 * If @key collates before the key of the current entry, there
231 		 * is definitely no such key in this index but we might need to
232 		 * descend into the B+tree so we just break out of the loop.
233 		 */
234 		if (rc == -1)
235 			break;
236 		/*
237 		 * A match should never happen as the memcmp() call should have
238 		 * cought it, but we still treat it correctly.
239 		 */
240 		if (!rc)
241 			goto ir_done;
242 		/* The keys are not equal, continue the search. */
243 	}
244 	/*
245 	 * We have finished with this index without success.  Check for the
246 	 * presence of a child node and if not present setup @ictx and return
247 	 * -ENOENT.
248 	 */
249 	if (!(ie->flags & INDEX_ENTRY_NODE)) {
250 		ntfs_debug("Entry not found.");
251 		err = -ENOENT;
252 		goto ir_done;
253 	} /* Child node present, descend into it. */
254 	/* Consistency check: Verify that an index allocation exists. */
255 	if (!NInoIndexAllocPresent(idx_ni)) {
256 		ntfs_error(sb, "No index allocation attribute but index entry "
257 				"requires one.  Inode 0x%lx is corrupt or "
258 				"driver bug.", idx_ni->mft_no);
259 		goto err_out;
260 	}
261 	/* Get the starting vcn of the index_block holding the child node. */
262 	vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
263 	ia_mapping = VFS_I(idx_ni)->i_mapping;
264 	/*
265 	 * We are done with the index root and the mft record.  Release them,
266 	 * otherwise we deadlock with ntfs_map_page().
267 	 */
268 	ntfs_attr_put_search_ctx(actx);
269 	unmap_mft_record(base_ni);
270 	m = NULL;
271 	actx = NULL;
272 descend_into_child_node:
273 	/*
274 	 * Convert vcn to index into the index allocation attribute in units
275 	 * of PAGE_SIZE and map the page cache page, reading it from
276 	 * disk if necessary.
277 	 */
278 	page = ntfs_map_page(ia_mapping, vcn <<
279 			idx_ni->itype.index.vcn_size_bits >> PAGE_SHIFT);
280 	if (IS_ERR(page)) {
281 		ntfs_error(sb, "Failed to map index page, error %ld.",
282 				-PTR_ERR(page));
283 		err = PTR_ERR(page);
284 		goto err_out;
285 	}
286 	lock_page(page);
287 	kaddr = (u8*)page_address(page);
288 fast_descend_into_child_node:
289 	/* Get to the index allocation block. */
290 	ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
291 			idx_ni->itype.index.vcn_size_bits) & ~PAGE_MASK));
292 	/* Bounds checks. */
293 	if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_SIZE) {
294 		ntfs_error(sb, "Out of bounds check failed.  Corrupt inode "
295 				"0x%lx or driver bug.", idx_ni->mft_no);
296 		goto unm_err_out;
297 	}
298 	/* Catch multi sector transfer fixup errors. */
299 	if (unlikely(!ntfs_is_indx_record(ia->magic))) {
300 		ntfs_error(sb, "Index record with vcn 0x%llx is corrupt.  "
301 				"Corrupt inode 0x%lx.  Run chkdsk.",
302 				(long long)vcn, idx_ni->mft_no);
303 		goto unm_err_out;
304 	}
305 	if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
306 		ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
307 				"different from expected VCN (0x%llx).  Inode "
308 				"0x%lx is corrupt or driver bug.",
309 				(unsigned long long)
310 				sle64_to_cpu(ia->index_block_vcn),
311 				(unsigned long long)vcn, idx_ni->mft_no);
312 		goto unm_err_out;
313 	}
314 	if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
315 			idx_ni->itype.index.block_size) {
316 		ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx has "
317 				"a size (%u) differing from the index "
318 				"specified size (%u).  Inode is corrupt or "
319 				"driver bug.", (unsigned long long)vcn,
320 				idx_ni->mft_no,
321 				le32_to_cpu(ia->index.allocated_size) + 0x18,
322 				idx_ni->itype.index.block_size);
323 		goto unm_err_out;
324 	}
325 	index_end = (u8*)ia + idx_ni->itype.index.block_size;
326 	if (index_end > kaddr + PAGE_SIZE) {
327 		ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx "
328 				"crosses page boundary.  Impossible!  Cannot "
329 				"access!  This is probably a bug in the "
330 				"driver.", (unsigned long long)vcn,
331 				idx_ni->mft_no);
332 		goto unm_err_out;
333 	}
334 	index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
335 	if (index_end > (u8*)ia + idx_ni->itype.index.block_size) {
336 		ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of inode "
337 				"0x%lx exceeds maximum size.",
338 				(unsigned long long)vcn, idx_ni->mft_no);
339 		goto unm_err_out;
340 	}
341 	/* The first index entry. */
342 	ie = (INDEX_ENTRY*)((u8*)&ia->index +
343 			le32_to_cpu(ia->index.entries_offset));
344 	/*
345 	 * Iterate similar to above big loop but applied to index buffer, thus
346 	 * loop until we exceed valid memory (corruption case) or until we
347 	 * reach the last entry.
348 	 */
349 	for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
350 		/* Bounds checks. */
351 		if ((u8*)ie < (u8*)ia || (u8*)ie +
352 				sizeof(INDEX_ENTRY_HEADER) > index_end ||
353 				(u8*)ie + le16_to_cpu(ie->length) > index_end) {
354 			ntfs_error(sb, "Index entry out of bounds in inode "
355 					"0x%lx.", idx_ni->mft_no);
356 			goto unm_err_out;
357 		}
358 		/*
359 		 * The last entry cannot contain a key.  It can however contain
360 		 * a pointer to a child node in the B+tree so we just break out.
361 		 */
362 		if (ie->flags & INDEX_ENTRY_END)
363 			break;
364 		/* Further bounds checks. */
365 		if ((u32)sizeof(INDEX_ENTRY_HEADER) +
366 				le16_to_cpu(ie->key_length) >
367 				le16_to_cpu(ie->data.vi.data_offset) ||
368 				(u32)le16_to_cpu(ie->data.vi.data_offset) +
369 				le16_to_cpu(ie->data.vi.data_length) >
370 				le16_to_cpu(ie->length)) {
371 			ntfs_error(sb, "Index entry out of bounds in inode "
372 					"0x%lx.", idx_ni->mft_no);
373 			goto unm_err_out;
374 		}
375 		/* If the keys match perfectly, we setup @ictx and return 0. */
376 		if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
377 				&ie->key, key_len)) {
378 ia_done:
379 			ictx->is_in_root = false;
380 			ictx->actx = NULL;
381 			ictx->base_ni = NULL;
382 			ictx->ia = ia;
383 			ictx->page = page;
384 			goto done;
385 		}
386 		/*
387 		 * Not a perfect match, need to do full blown collation so we
388 		 * know which way in the B+tree we have to go.
389 		 */
390 		rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
391 				key_len, &ie->key, le16_to_cpu(ie->key_length));
392 		/*
393 		 * If @key collates before the key of the current entry, there
394 		 * is definitely no such key in this index but we might need to
395 		 * descend into the B+tree so we just break out of the loop.
396 		 */
397 		if (rc == -1)
398 			break;
399 		/*
400 		 * A match should never happen as the memcmp() call should have
401 		 * cought it, but we still treat it correctly.
402 		 */
403 		if (!rc)
404 			goto ia_done;
405 		/* The keys are not equal, continue the search. */
406 	}
407 	/*
408 	 * We have finished with this index buffer without success.  Check for
409 	 * the presence of a child node and if not present return -ENOENT.
410 	 */
411 	if (!(ie->flags & INDEX_ENTRY_NODE)) {
412 		ntfs_debug("Entry not found.");
413 		err = -ENOENT;
414 		goto ia_done;
415 	}
416 	if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
417 		ntfs_error(sb, "Index entry with child node found in a leaf "
418 				"node in inode 0x%lx.", idx_ni->mft_no);
419 		goto unm_err_out;
420 	}
421 	/* Child node present, descend into it. */
422 	old_vcn = vcn;
423 	vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
424 	if (vcn >= 0) {
425 		/*
426 		 * If vcn is in the same page cache page as old_vcn we recycle
427 		 * the mapped page.
428 		 */
429 		if (old_vcn << vol->cluster_size_bits >>
430 				PAGE_SHIFT == vcn <<
431 				vol->cluster_size_bits >>
432 				PAGE_SHIFT)
433 			goto fast_descend_into_child_node;
434 		unlock_page(page);
435 		ntfs_unmap_page(page);
436 		goto descend_into_child_node;
437 	}
438 	ntfs_error(sb, "Negative child node vcn in inode 0x%lx.",
439 			idx_ni->mft_no);
440 unm_err_out:
441 	unlock_page(page);
442 	ntfs_unmap_page(page);
443 err_out:
444 	if (!err)
445 		err = -EIO;
446 	if (actx)
447 		ntfs_attr_put_search_ctx(actx);
448 	if (m)
449 		unmap_mft_record(base_ni);
450 	return err;
451 idx_err_out:
452 	ntfs_error(sb, "Corrupt index.  Aborting lookup.");
453 	goto err_out;
454 }
455