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Linux/fs/ntfs/index.c

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  1 // SPDX-License-Identifier: GPL-2.0-or-later
  2 /*
  3  * index.c - NTFS kernel index handling.  Part of the Linux-NTFS project.
  4  *
  5  * Copyright (c) 2004-2005 Anton Altaparmakov
  6  */
  7 
  8 #include <linux/slab.h>
  9 
 10 #include "aops.h"
 11 #include "collate.h"
 12 #include "debug.h"
 13 #include "index.h"
 14 #include "ntfs.h"
 15 
 16 /**
 17  * ntfs_index_ctx_get - allocate and initialize a new index context
 18  * @idx_ni:     ntfs index inode with which to initialize the context
 19  *
 20  * Allocate a new index context, initialize it with @idx_ni and return it.
 21  * Return NULL if allocation failed.
 22  *
 23  * Locking:  Caller must hold i_mutex on the index inode.
 24  */
 25 ntfs_index_context *ntfs_index_ctx_get(ntfs_inode *idx_ni)
 26 {
 27         ntfs_index_context *ictx;
 28 
 29         ictx = kmem_cache_alloc(ntfs_index_ctx_cache, GFP_NOFS);
 30         if (ictx)
 31                 *ictx = (ntfs_index_context){ .idx_ni = idx_ni };
 32         return ictx;
 33 }
 34 
 35 /**
 36  * ntfs_index_ctx_put - release an index context
 37  * @ictx:       index context to free
 38  *
 39  * Release the index context @ictx, releasing all associated resources.
 40  *
 41  * Locking:  Caller must hold i_mutex on the index inode.
 42  */
 43 void ntfs_index_ctx_put(ntfs_index_context *ictx)
 44 {
 45         if (ictx->entry) {
 46                 if (ictx->is_in_root) {
 47                         if (ictx->actx)
 48                                 ntfs_attr_put_search_ctx(ictx->actx);
 49                         if (ictx->base_ni)
 50                                 unmap_mft_record(ictx->base_ni);
 51                 } else {
 52                         struct page *page = ictx->page;
 53                         if (page) {
 54                                 BUG_ON(!PageLocked(page));
 55                                 unlock_page(page);
 56                                 ntfs_unmap_page(page);
 57                         }
 58                 }
 59         }
 60         kmem_cache_free(ntfs_index_ctx_cache, ictx);
 61         return;
 62 }
 63 
 64 /**
 65  * ntfs_index_lookup - find a key in an index and return its index entry
 66  * @key:        [IN] key for which to search in the index
 67  * @key_len:    [IN] length of @key in bytes
 68  * @ictx:       [IN/OUT] context describing the index and the returned entry
 69  *
 70  * Before calling ntfs_index_lookup(), @ictx must have been obtained from a
 71  * call to ntfs_index_ctx_get().
 72  *
 73  * Look for the @key in the index specified by the index lookup context @ictx.
 74  * ntfs_index_lookup() walks the contents of the index looking for the @key.
 75  *
 76  * If the @key is found in the index, 0 is returned and @ictx is setup to
 77  * describe the index entry containing the matching @key.  @ictx->entry is the
 78  * index entry and @ictx->data and @ictx->data_len are the index entry data and
 79  * its length in bytes, respectively.
 80  *
 81  * If the @key is not found in the index, -ENOENT is returned and @ictx is
 82  * setup to describe the index entry whose key collates immediately after the
 83  * search @key, i.e. this is the position in the index at which an index entry
 84  * with a key of @key would need to be inserted.
 85  *
 86  * If an error occurs return the negative error code and @ictx is left
 87  * untouched.
 88  *
 89  * When finished with the entry and its data, call ntfs_index_ctx_put() to free
 90  * the context and other associated resources.
 91  *
 92  * If the index entry was modified, call flush_dcache_index_entry_page()
 93  * immediately after the modification and either ntfs_index_entry_mark_dirty()
 94  * or ntfs_index_entry_write() before the call to ntfs_index_ctx_put() to
 95  * ensure that the changes are written to disk.
 96  *
 97  * Locking:  - Caller must hold i_mutex on the index inode.
 98  *           - Each page cache page in the index allocation mapping must be
 99  *             locked whilst being accessed otherwise we may find a corrupt
100  *             page due to it being under ->writepage at the moment which
101  *             applies the mst protection fixups before writing out and then
102  *             removes them again after the write is complete after which it 
103  *             unlocks the page.
104  */
105 int ntfs_index_lookup(const void *key, const int key_len,
106                 ntfs_index_context *ictx)
107 {
108         VCN vcn, old_vcn;
109         ntfs_inode *idx_ni = ictx->idx_ni;
110         ntfs_volume *vol = idx_ni->vol;
111         struct super_block *sb = vol->sb;
112         ntfs_inode *base_ni = idx_ni->ext.base_ntfs_ino;
113         MFT_RECORD *m;
114         INDEX_ROOT *ir;
115         INDEX_ENTRY *ie;
116         INDEX_ALLOCATION *ia;
117         u8 *index_end, *kaddr;
118         ntfs_attr_search_ctx *actx;
119         struct address_space *ia_mapping;
120         struct page *page;
121         int rc, err = 0;
122 
123         ntfs_debug("Entering.");
124         BUG_ON(!NInoAttr(idx_ni));
125         BUG_ON(idx_ni->type != AT_INDEX_ALLOCATION);
126         BUG_ON(idx_ni->nr_extents != -1);
127         BUG_ON(!base_ni);
128         BUG_ON(!key);
129         BUG_ON(key_len <= 0);
130         if (!ntfs_is_collation_rule_supported(
131                         idx_ni->itype.index.collation_rule)) {
132                 ntfs_error(sb, "Index uses unsupported collation rule 0x%x.  "
133                                 "Aborting lookup.", le32_to_cpu(
134                                 idx_ni->itype.index.collation_rule));
135                 return -EOPNOTSUPP;
136         }
137         /* Get hold of the mft record for the index inode. */
138         m = map_mft_record(base_ni);
139         if (IS_ERR(m)) {
140                 ntfs_error(sb, "map_mft_record() failed with error code %ld.",
141                                 -PTR_ERR(m));
142                 return PTR_ERR(m);
143         }
144         actx = ntfs_attr_get_search_ctx(base_ni, m);
145         if (unlikely(!actx)) {
146                 err = -ENOMEM;
147                 goto err_out;
148         }
149         /* Find the index root attribute in the mft record. */
150         err = ntfs_attr_lookup(AT_INDEX_ROOT, idx_ni->name, idx_ni->name_len,
151                         CASE_SENSITIVE, 0, NULL, 0, actx);
152         if (unlikely(err)) {
153                 if (err == -ENOENT) {
154                         ntfs_error(sb, "Index root attribute missing in inode "
155                                         "0x%lx.", idx_ni->mft_no);
156                         err = -EIO;
157                 }
158                 goto err_out;
159         }
160         /* Get to the index root value (it has been verified in read_inode). */
161         ir = (INDEX_ROOT*)((u8*)actx->attr +
162                         le16_to_cpu(actx->attr->data.resident.value_offset));
163         index_end = (u8*)&ir->index + le32_to_cpu(ir->index.index_length);
164         /* The first index entry. */
165         ie = (INDEX_ENTRY*)((u8*)&ir->index +
166                         le32_to_cpu(ir->index.entries_offset));
167         /*
168          * Loop until we exceed valid memory (corruption case) or until we
169          * reach the last entry.
170          */
171         for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
172                 /* Bounds checks. */
173                 if ((u8*)ie < (u8*)actx->mrec || (u8*)ie +
174                                 sizeof(INDEX_ENTRY_HEADER) > index_end ||
175                                 (u8*)ie + le16_to_cpu(ie->length) > index_end)
176                         goto idx_err_out;
177                 /*
178                  * The last entry cannot contain a key.  It can however contain
179                  * a pointer to a child node in the B+tree so we just break out.
180                  */
181                 if (ie->flags & INDEX_ENTRY_END)
182                         break;
183                 /* Further bounds checks. */
184                 if ((u32)sizeof(INDEX_ENTRY_HEADER) +
185                                 le16_to_cpu(ie->key_length) >
186                                 le16_to_cpu(ie->data.vi.data_offset) ||
187                                 (u32)le16_to_cpu(ie->data.vi.data_offset) +
188                                 le16_to_cpu(ie->data.vi.data_length) >
189                                 le16_to_cpu(ie->length))
190                         goto idx_err_out;
191                 /* If the keys match perfectly, we setup @ictx and return 0. */
192                 if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
193                                 &ie->key, key_len)) {
194 ir_done:
195                         ictx->is_in_root = true;
196                         ictx->ir = ir;
197                         ictx->actx = actx;
198                         ictx->base_ni = base_ni;
199                         ictx->ia = NULL;
200                         ictx->page = NULL;
201 done:
202                         ictx->entry = ie;
203                         ictx->data = (u8*)ie +
204                                         le16_to_cpu(ie->data.vi.data_offset);
205                         ictx->data_len = le16_to_cpu(ie->data.vi.data_length);
206                         ntfs_debug("Done.");
207                         return err;
208                 }
209                 /*
210                  * Not a perfect match, need to do full blown collation so we
211                  * know which way in the B+tree we have to go.
212                  */
213                 rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
214                                 key_len, &ie->key, le16_to_cpu(ie->key_length));
215                 /*
216                  * If @key collates before the key of the current entry, there
217                  * is definitely no such key in this index but we might need to
218                  * descend into the B+tree so we just break out of the loop.
219                  */
220                 if (rc == -1)
221                         break;
222                 /*
223                  * A match should never happen as the memcmp() call should have
224                  * cought it, but we still treat it correctly.
225                  */
226                 if (!rc)
227                         goto ir_done;
228                 /* The keys are not equal, continue the search. */
229         }
230         /*
231          * We have finished with this index without success.  Check for the
232          * presence of a child node and if not present setup @ictx and return
233          * -ENOENT.
234          */
235         if (!(ie->flags & INDEX_ENTRY_NODE)) {
236                 ntfs_debug("Entry not found.");
237                 err = -ENOENT;
238                 goto ir_done;
239         } /* Child node present, descend into it. */
240         /* Consistency check: Verify that an index allocation exists. */
241         if (!NInoIndexAllocPresent(idx_ni)) {
242                 ntfs_error(sb, "No index allocation attribute but index entry "
243                                 "requires one.  Inode 0x%lx is corrupt or "
244                                 "driver bug.", idx_ni->mft_no);
245                 goto err_out;
246         }
247         /* Get the starting vcn of the index_block holding the child node. */
248         vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
249         ia_mapping = VFS_I(idx_ni)->i_mapping;
250         /*
251          * We are done with the index root and the mft record.  Release them,
252          * otherwise we deadlock with ntfs_map_page().
253          */
254         ntfs_attr_put_search_ctx(actx);
255         unmap_mft_record(base_ni);
256         m = NULL;
257         actx = NULL;
258 descend_into_child_node:
259         /*
260          * Convert vcn to index into the index allocation attribute in units
261          * of PAGE_SIZE and map the page cache page, reading it from
262          * disk if necessary.
263          */
264         page = ntfs_map_page(ia_mapping, vcn <<
265                         idx_ni->itype.index.vcn_size_bits >> PAGE_SHIFT);
266         if (IS_ERR(page)) {
267                 ntfs_error(sb, "Failed to map index page, error %ld.",
268                                 -PTR_ERR(page));
269                 err = PTR_ERR(page);
270                 goto err_out;
271         }
272         lock_page(page);
273         kaddr = (u8*)page_address(page);
274 fast_descend_into_child_node:
275         /* Get to the index allocation block. */
276         ia = (INDEX_ALLOCATION*)(kaddr + ((vcn <<
277                         idx_ni->itype.index.vcn_size_bits) & ~PAGE_MASK));
278         /* Bounds checks. */
279         if ((u8*)ia < kaddr || (u8*)ia > kaddr + PAGE_SIZE) {
280                 ntfs_error(sb, "Out of bounds check failed.  Corrupt inode "
281                                 "0x%lx or driver bug.", idx_ni->mft_no);
282                 goto unm_err_out;
283         }
284         /* Catch multi sector transfer fixup errors. */
285         if (unlikely(!ntfs_is_indx_record(ia->magic))) {
286                 ntfs_error(sb, "Index record with vcn 0x%llx is corrupt.  "
287                                 "Corrupt inode 0x%lx.  Run chkdsk.",
288                                 (long long)vcn, idx_ni->mft_no);
289                 goto unm_err_out;
290         }
291         if (sle64_to_cpu(ia->index_block_vcn) != vcn) {
292                 ntfs_error(sb, "Actual VCN (0x%llx) of index buffer is "
293                                 "different from expected VCN (0x%llx).  Inode "
294                                 "0x%lx is corrupt or driver bug.",
295                                 (unsigned long long)
296                                 sle64_to_cpu(ia->index_block_vcn),
297                                 (unsigned long long)vcn, idx_ni->mft_no);
298                 goto unm_err_out;
299         }
300         if (le32_to_cpu(ia->index.allocated_size) + 0x18 !=
301                         idx_ni->itype.index.block_size) {
302                 ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx has "
303                                 "a size (%u) differing from the index "
304                                 "specified size (%u).  Inode is corrupt or "
305                                 "driver bug.", (unsigned long long)vcn,
306                                 idx_ni->mft_no,
307                                 le32_to_cpu(ia->index.allocated_size) + 0x18,
308                                 idx_ni->itype.index.block_size);
309                 goto unm_err_out;
310         }
311         index_end = (u8*)ia + idx_ni->itype.index.block_size;
312         if (index_end > kaddr + PAGE_SIZE) {
313                 ntfs_error(sb, "Index buffer (VCN 0x%llx) of inode 0x%lx "
314                                 "crosses page boundary.  Impossible!  Cannot "
315                                 "access!  This is probably a bug in the "
316                                 "driver.", (unsigned long long)vcn,
317                                 idx_ni->mft_no);
318                 goto unm_err_out;
319         }
320         index_end = (u8*)&ia->index + le32_to_cpu(ia->index.index_length);
321         if (index_end > (u8*)ia + idx_ni->itype.index.block_size) {
322                 ntfs_error(sb, "Size of index buffer (VCN 0x%llx) of inode "
323                                 "0x%lx exceeds maximum size.",
324                                 (unsigned long long)vcn, idx_ni->mft_no);
325                 goto unm_err_out;
326         }
327         /* The first index entry. */
328         ie = (INDEX_ENTRY*)((u8*)&ia->index +
329                         le32_to_cpu(ia->index.entries_offset));
330         /*
331          * Iterate similar to above big loop but applied to index buffer, thus
332          * loop until we exceed valid memory (corruption case) or until we
333          * reach the last entry.
334          */
335         for (;; ie = (INDEX_ENTRY*)((u8*)ie + le16_to_cpu(ie->length))) {
336                 /* Bounds checks. */
337                 if ((u8*)ie < (u8*)ia || (u8*)ie +
338                                 sizeof(INDEX_ENTRY_HEADER) > index_end ||
339                                 (u8*)ie + le16_to_cpu(ie->length) > index_end) {
340                         ntfs_error(sb, "Index entry out of bounds in inode "
341                                         "0x%lx.", idx_ni->mft_no);
342                         goto unm_err_out;
343                 }
344                 /*
345                  * The last entry cannot contain a key.  It can however contain
346                  * a pointer to a child node in the B+tree so we just break out.
347                  */
348                 if (ie->flags & INDEX_ENTRY_END)
349                         break;
350                 /* Further bounds checks. */
351                 if ((u32)sizeof(INDEX_ENTRY_HEADER) +
352                                 le16_to_cpu(ie->key_length) >
353                                 le16_to_cpu(ie->data.vi.data_offset) ||
354                                 (u32)le16_to_cpu(ie->data.vi.data_offset) +
355                                 le16_to_cpu(ie->data.vi.data_length) >
356                                 le16_to_cpu(ie->length)) {
357                         ntfs_error(sb, "Index entry out of bounds in inode "
358                                         "0x%lx.", idx_ni->mft_no);
359                         goto unm_err_out;
360                 }
361                 /* If the keys match perfectly, we setup @ictx and return 0. */
362                 if ((key_len == le16_to_cpu(ie->key_length)) && !memcmp(key,
363                                 &ie->key, key_len)) {
364 ia_done:
365                         ictx->is_in_root = false;
366                         ictx->actx = NULL;
367                         ictx->base_ni = NULL;
368                         ictx->ia = ia;
369                         ictx->page = page;
370                         goto done;
371                 }
372                 /*
373                  * Not a perfect match, need to do full blown collation so we
374                  * know which way in the B+tree we have to go.
375                  */
376                 rc = ntfs_collate(vol, idx_ni->itype.index.collation_rule, key,
377                                 key_len, &ie->key, le16_to_cpu(ie->key_length));
378                 /*
379                  * If @key collates before the key of the current entry, there
380                  * is definitely no such key in this index but we might need to
381                  * descend into the B+tree so we just break out of the loop.
382                  */
383                 if (rc == -1)
384                         break;
385                 /*
386                  * A match should never happen as the memcmp() call should have
387                  * cought it, but we still treat it correctly.
388                  */
389                 if (!rc)
390                         goto ia_done;
391                 /* The keys are not equal, continue the search. */
392         }
393         /*
394          * We have finished with this index buffer without success.  Check for
395          * the presence of a child node and if not present return -ENOENT.
396          */
397         if (!(ie->flags & INDEX_ENTRY_NODE)) {
398                 ntfs_debug("Entry not found.");
399                 err = -ENOENT;
400                 goto ia_done;
401         }
402         if ((ia->index.flags & NODE_MASK) == LEAF_NODE) {
403                 ntfs_error(sb, "Index entry with child node found in a leaf "
404                                 "node in inode 0x%lx.", idx_ni->mft_no);
405                 goto unm_err_out;
406         }
407         /* Child node present, descend into it. */
408         old_vcn = vcn;
409         vcn = sle64_to_cpup((sle64*)((u8*)ie + le16_to_cpu(ie->length) - 8));
410         if (vcn >= 0) {
411                 /*
412                  * If vcn is in the same page cache page as old_vcn we recycle
413                  * the mapped page.
414                  */
415                 if (old_vcn << vol->cluster_size_bits >>
416                                 PAGE_SHIFT == vcn <<
417                                 vol->cluster_size_bits >>
418                                 PAGE_SHIFT)
419                         goto fast_descend_into_child_node;
420                 unlock_page(page);
421                 ntfs_unmap_page(page);
422                 goto descend_into_child_node;
423         }
424         ntfs_error(sb, "Negative child node vcn in inode 0x%lx.",
425                         idx_ni->mft_no);
426 unm_err_out:
427         unlock_page(page);
428         ntfs_unmap_page(page);
429 err_out:
430         if (!err)
431                 err = -EIO;
432         if (actx)
433                 ntfs_attr_put_search_ctx(actx);
434         if (m)
435                 unmap_mft_record(base_ni);
436         return err;
437 idx_err_out:
438         ntfs_error(sb, "Corrupt index.  Aborting lookup.");
439         goto err_out;
440 }
441 

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