Root/fs/ntfs/index.c

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 */
39ntfs_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 */
57void 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 */
119int 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)) {
208ir_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;
215done:
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;
272descend_into_child_node:
273    /*
274     * Convert vcn to index into the index allocation attribute in units
275     * of PAGE_CACHE_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_CACHE_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);
288fast_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_CACHE_MASK));
292    /* Bounds checks. */
293    if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_CACHE_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_CACHE_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)) {
378ia_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_CACHE_SHIFT == vcn <<
431                vol->cluster_size_bits >>
432                PAGE_CACHE_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);
440unm_err_out:
441    unlock_page(page);
442    ntfs_unmap_page(page);
443err_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;
451idx_err_out:
452    ntfs_error(sb, "Corrupt index. Aborting lookup.");
453    goto err_out;
454}
455

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