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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/ext4/verity.c: fs-verity support for ext4
4 *
5 * Copyright 2019 Google LLC
6 */
7
8/*
9 * Implementation of fsverity_operations for ext4.
10 *
11 * ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
12 * the end of the file, starting at the first 64K boundary beyond i_size. This
13 * approach works because (a) verity files are readonly, and (b) pages fully
14 * beyond i_size aren't visible to userspace but can be read/written internally
15 * by ext4 with only some relatively small changes to ext4. This approach
16 * avoids having to depend on the EA_INODE feature and on rearchitecturing
17 * ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
18 * to support encrypting xattrs. Note that the verity metadata *must* be
19 * encrypted when the file is, since it contains hashes of the plaintext data.
20 *
21 * Using a 64K boundary rather than a 4K one keeps things ready for
22 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
23 * since there can be a hole between i_size and the start of the Merkle tree.
24 */
25
26#include <linux/quotaops.h>
27
28#include "ext4.h"
29#include "ext4_extents.h"
30#include "ext4_jbd2.h"
31
32static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
33{
34 return round_up(inode->i_size, 65536);
35}
36
37/*
38 * Read some verity metadata from the inode. __vfs_read() can't be used because
39 * we need to read beyond i_size.
40 */
41static int pagecache_read(struct inode *inode, void *buf, size_t count,
42 loff_t pos)
43{
44 while (count) {
45 size_t n = min_t(size_t, count,
46 PAGE_SIZE - offset_in_page(pos));
47 struct page *page;
48
49 page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
50 NULL);
51 if (IS_ERR(page))
52 return PTR_ERR(page);
53
54 memcpy_from_page(buf, page, offset_in_page(pos), n);
55
56 put_page(page);
57
58 buf += n;
59 pos += n;
60 count -= n;
61 }
62 return 0;
63}
64
65/*
66 * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
67 * kernel_write() can't be used because the file descriptor is readonly.
68 */
69static int pagecache_write(struct inode *inode, const void *buf, size_t count,
70 loff_t pos)
71{
72 struct address_space *mapping = inode->i_mapping;
73 const struct address_space_operations *aops = mapping->a_ops;
74
75 if (pos + count > inode->i_sb->s_maxbytes)
76 return -EFBIG;
77
78 while (count) {
79 size_t n = min_t(size_t, count,
80 PAGE_SIZE - offset_in_page(pos));
81 struct page *page;
82 void *fsdata = NULL;
83 int res;
84
85 res = aops->write_begin(NULL, mapping, pos, n, &page, &fsdata);
86 if (res)
87 return res;
88
89 memcpy_to_page(page, offset_in_page(pos), buf, n);
90
91 res = aops->write_end(NULL, mapping, pos, n, n, page, fsdata);
92 if (res < 0)
93 return res;
94 if (res != n)
95 return -EIO;
96
97 buf += n;
98 pos += n;
99 count -= n;
100 }
101 return 0;
102}
103
104static int ext4_begin_enable_verity(struct file *filp)
105{
106 struct inode *inode = file_inode(filp);
107 const int credits = 2; /* superblock and inode for ext4_orphan_add() */
108 handle_t *handle;
109 int err;
110
111 if (IS_DAX(inode) || ext4_test_inode_flag(inode, EXT4_INODE_DAX))
112 return -EINVAL;
113
114 if (ext4_verity_in_progress(inode))
115 return -EBUSY;
116
117 /*
118 * Since the file was opened readonly, we have to initialize the jbd
119 * inode and quotas here and not rely on ->open() doing it. This must
120 * be done before evicting the inline data.
121 */
122
123 err = ext4_inode_attach_jinode(inode);
124 if (err)
125 return err;
126
127 err = dquot_initialize(inode);
128 if (err)
129 return err;
130
131 err = ext4_convert_inline_data(inode);
132 if (err)
133 return err;
134
135 if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
136 ext4_warning_inode(inode,
137 "verity is only allowed on extent-based files");
138 return -EOPNOTSUPP;
139 }
140
141 /*
142 * ext4 uses the last allocated block to find the verity descriptor, so
143 * we must remove any other blocks past EOF which might confuse things.
144 */
145 err = ext4_truncate(inode);
146 if (err)
147 return err;
148
149 handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
150 if (IS_ERR(handle))
151 return PTR_ERR(handle);
152
153 err = ext4_orphan_add(handle, inode);
154 if (err == 0)
155 ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
156
157 ext4_journal_stop(handle);
158 return err;
159}
160
161/*
162 * ext4 stores the verity descriptor beginning on the next filesystem block
163 * boundary after the Merkle tree. Then, the descriptor size is stored in the
164 * last 4 bytes of the last allocated filesystem block --- which is either the
165 * block in which the descriptor ends, or the next block after that if there
166 * weren't at least 4 bytes remaining.
167 *
168 * We can't simply store the descriptor in an xattr because it *must* be
169 * encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
170 * xattrs. Also, if the descriptor includes a large signature blob it may be
171 * too large to store in an xattr without the EA_INODE feature.
172 */
173static int ext4_write_verity_descriptor(struct inode *inode, const void *desc,
174 size_t desc_size, u64 merkle_tree_size)
175{
176 const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
177 merkle_tree_size, i_blocksize(inode));
178 const u64 desc_end = desc_pos + desc_size;
179 const __le32 desc_size_disk = cpu_to_le32(desc_size);
180 const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
181 i_blocksize(inode)) -
182 sizeof(desc_size_disk);
183 int err;
184
185 err = pagecache_write(inode, desc, desc_size, desc_pos);
186 if (err)
187 return err;
188
189 return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
190 desc_size_pos);
191}
192
193static int ext4_end_enable_verity(struct file *filp, const void *desc,
194 size_t desc_size, u64 merkle_tree_size)
195{
196 struct inode *inode = file_inode(filp);
197 const int credits = 2; /* superblock and inode for ext4_orphan_del() */
198 handle_t *handle;
199 struct ext4_iloc iloc;
200 int err = 0;
201
202 /*
203 * If an error already occurred (which fs/verity/ signals by passing
204 * desc == NULL), then only clean-up is needed.
205 */
206 if (desc == NULL)
207 goto cleanup;
208
209 /* Append the verity descriptor. */
210 err = ext4_write_verity_descriptor(inode, desc, desc_size,
211 merkle_tree_size);
212 if (err)
213 goto cleanup;
214
215 /*
216 * Write all pages (both data and verity metadata). Note that this must
217 * happen before clearing EXT4_STATE_VERITY_IN_PROGRESS; otherwise pages
218 * beyond i_size won't be written properly. For crash consistency, this
219 * also must happen before the verity inode flag gets persisted.
220 */
221 err = filemap_write_and_wait(inode->i_mapping);
222 if (err)
223 goto cleanup;
224
225 /*
226 * Finally, set the verity inode flag and remove the inode from the
227 * orphan list (in a single transaction).
228 */
229
230 handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
231 if (IS_ERR(handle)) {
232 err = PTR_ERR(handle);
233 goto cleanup;
234 }
235
236 err = ext4_orphan_del(handle, inode);
237 if (err)
238 goto stop_and_cleanup;
239
240 err = ext4_reserve_inode_write(handle, inode, &iloc);
241 if (err)
242 goto stop_and_cleanup;
243
244 ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
245 ext4_set_inode_flags(inode, false);
246 err = ext4_mark_iloc_dirty(handle, inode, &iloc);
247 if (err)
248 goto stop_and_cleanup;
249
250 ext4_journal_stop(handle);
251
252 ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
253 return 0;
254
255stop_and_cleanup:
256 ext4_journal_stop(handle);
257cleanup:
258 /*
259 * Verity failed to be enabled, so clean up by truncating any verity
260 * metadata that was written beyond i_size (both from cache and from
261 * disk), removing the inode from the orphan list (if it wasn't done
262 * already), and clearing EXT4_STATE_VERITY_IN_PROGRESS.
263 */
264 truncate_inode_pages(inode->i_mapping, inode->i_size);
265 ext4_truncate(inode);
266 ext4_orphan_del(NULL, inode);
267 ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
268 return err;
269}
270
271static int ext4_get_verity_descriptor_location(struct inode *inode,
272 size_t *desc_size_ret,
273 u64 *desc_pos_ret)
274{
275 struct ext4_ext_path *path;
276 struct ext4_extent *last_extent;
277 u32 end_lblk;
278 u64 desc_size_pos;
279 __le32 desc_size_disk;
280 u32 desc_size;
281 u64 desc_pos;
282 int err;
283
284 /*
285 * Descriptor size is in last 4 bytes of last allocated block.
286 * See ext4_write_verity_descriptor().
287 */
288
289 if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
290 EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
291 return -EFSCORRUPTED;
292 }
293
294 path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
295 if (IS_ERR(path))
296 return PTR_ERR(path);
297
298 last_extent = path[path->p_depth].p_ext;
299 if (!last_extent) {
300 EXT4_ERROR_INODE(inode, "verity file has no extents");
301 ext4_free_ext_path(path);
302 return -EFSCORRUPTED;
303 }
304
305 end_lblk = le32_to_cpu(last_extent->ee_block) +
306 ext4_ext_get_actual_len(last_extent);
307 desc_size_pos = (u64)end_lblk << inode->i_blkbits;
308 ext4_free_ext_path(path);
309
310 if (desc_size_pos < sizeof(desc_size_disk))
311 goto bad;
312 desc_size_pos -= sizeof(desc_size_disk);
313
314 err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
315 desc_size_pos);
316 if (err)
317 return err;
318 desc_size = le32_to_cpu(desc_size_disk);
319
320 /*
321 * The descriptor is stored just before the desc_size_disk, but starting
322 * on a filesystem block boundary.
323 */
324
325 if (desc_size > INT_MAX || desc_size > desc_size_pos)
326 goto bad;
327
328 desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
329 if (desc_pos < ext4_verity_metadata_pos(inode))
330 goto bad;
331
332 *desc_size_ret = desc_size;
333 *desc_pos_ret = desc_pos;
334 return 0;
335
336bad:
337 EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
338 return -EFSCORRUPTED;
339}
340
341static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
342 size_t buf_size)
343{
344 size_t desc_size = 0;
345 u64 desc_pos = 0;
346 int err;
347
348 err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
349 if (err)
350 return err;
351
352 if (buf_size) {
353 if (desc_size > buf_size)
354 return -ERANGE;
355 err = pagecache_read(inode, buf, desc_size, desc_pos);
356 if (err)
357 return err;
358 }
359 return desc_size;
360}
361
362static struct page *ext4_read_merkle_tree_page(struct inode *inode,
363 pgoff_t index,
364 unsigned long num_ra_pages)
365{
366 struct page *page;
367
368 index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
369
370 page = find_get_page_flags(inode->i_mapping, index, FGP_ACCESSED);
371 if (!page || !PageUptodate(page)) {
372 DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
373
374 if (page)
375 put_page(page);
376 else if (num_ra_pages > 1)
377 page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
378 page = read_mapping_page(inode->i_mapping, index, NULL);
379 }
380 return page;
381}
382
383static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
384 u64 index, int log_blocksize)
385{
386 loff_t pos = ext4_verity_metadata_pos(inode) + (index << log_blocksize);
387
388 return pagecache_write(inode, buf, 1 << log_blocksize, pos);
389}
390
391const struct fsverity_operations ext4_verityops = {
392 .begin_enable_verity = ext4_begin_enable_verity,
393 .end_enable_verity = ext4_end_enable_verity,
394 .get_verity_descriptor = ext4_get_verity_descriptor,
395 .read_merkle_tree_page = ext4_read_merkle_tree_page,
396 .write_merkle_tree_block = ext4_write_merkle_tree_block,
397};
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/ext4/verity.c: fs-verity support for ext4
4 *
5 * Copyright 2019 Google LLC
6 */
7
8/*
9 * Implementation of fsverity_operations for ext4.
10 *
11 * ext4 stores the verity metadata (Merkle tree and fsverity_descriptor) past
12 * the end of the file, starting at the first 64K boundary beyond i_size. This
13 * approach works because (a) verity files are readonly, and (b) pages fully
14 * beyond i_size aren't visible to userspace but can be read/written internally
15 * by ext4 with only some relatively small changes to ext4. This approach
16 * avoids having to depend on the EA_INODE feature and on rearchitecturing
17 * ext4's xattr support to support paging multi-gigabyte xattrs into memory, and
18 * to support encrypting xattrs. Note that the verity metadata *must* be
19 * encrypted when the file is, since it contains hashes of the plaintext data.
20 *
21 * Using a 64K boundary rather than a 4K one keeps things ready for
22 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
23 * since there can be a hole between i_size and the start of the Merkle tree.
24 */
25
26#include <linux/quotaops.h>
27
28#include "ext4.h"
29#include "ext4_extents.h"
30#include "ext4_jbd2.h"
31
32static inline loff_t ext4_verity_metadata_pos(const struct inode *inode)
33{
34 return round_up(inode->i_size, 65536);
35}
36
37/*
38 * Read some verity metadata from the inode. __vfs_read() can't be used because
39 * we need to read beyond i_size.
40 */
41static int pagecache_read(struct inode *inode, void *buf, size_t count,
42 loff_t pos)
43{
44 while (count) {
45 size_t n = min_t(size_t, count,
46 PAGE_SIZE - offset_in_page(pos));
47 struct page *page;
48 void *addr;
49
50 page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
51 NULL);
52 if (IS_ERR(page))
53 return PTR_ERR(page);
54
55 addr = kmap_atomic(page);
56 memcpy(buf, addr + offset_in_page(pos), n);
57 kunmap_atomic(addr);
58
59 put_page(page);
60
61 buf += n;
62 pos += n;
63 count -= n;
64 }
65 return 0;
66}
67
68/*
69 * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
70 * kernel_write() can't be used because the file descriptor is readonly.
71 */
72static int pagecache_write(struct inode *inode, const void *buf, size_t count,
73 loff_t pos)
74{
75 if (pos + count > inode->i_sb->s_maxbytes)
76 return -EFBIG;
77
78 while (count) {
79 size_t n = min_t(size_t, count,
80 PAGE_SIZE - offset_in_page(pos));
81 struct page *page;
82 void *fsdata;
83 void *addr;
84 int res;
85
86 res = pagecache_write_begin(NULL, inode->i_mapping, pos, n, 0,
87 &page, &fsdata);
88 if (res)
89 return res;
90
91 addr = kmap_atomic(page);
92 memcpy(addr + offset_in_page(pos), buf, n);
93 kunmap_atomic(addr);
94
95 res = pagecache_write_end(NULL, inode->i_mapping, pos, n, n,
96 page, fsdata);
97 if (res < 0)
98 return res;
99 if (res != n)
100 return -EIO;
101
102 buf += n;
103 pos += n;
104 count -= n;
105 }
106 return 0;
107}
108
109static int ext4_begin_enable_verity(struct file *filp)
110{
111 struct inode *inode = file_inode(filp);
112 const int credits = 2; /* superblock and inode for ext4_orphan_add() */
113 handle_t *handle;
114 int err;
115
116 if (ext4_verity_in_progress(inode))
117 return -EBUSY;
118
119 /*
120 * Since the file was opened readonly, we have to initialize the jbd
121 * inode and quotas here and not rely on ->open() doing it. This must
122 * be done before evicting the inline data.
123 */
124
125 err = ext4_inode_attach_jinode(inode);
126 if (err)
127 return err;
128
129 err = dquot_initialize(inode);
130 if (err)
131 return err;
132
133 err = ext4_convert_inline_data(inode);
134 if (err)
135 return err;
136
137 if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
138 ext4_warning_inode(inode,
139 "verity is only allowed on extent-based files");
140 return -EOPNOTSUPP;
141 }
142
143 /*
144 * ext4 uses the last allocated block to find the verity descriptor, so
145 * we must remove any other blocks past EOF which might confuse things.
146 */
147 err = ext4_truncate(inode);
148 if (err)
149 return err;
150
151 handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
152 if (IS_ERR(handle))
153 return PTR_ERR(handle);
154
155 err = ext4_orphan_add(handle, inode);
156 if (err == 0)
157 ext4_set_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
158
159 ext4_journal_stop(handle);
160 return err;
161}
162
163/*
164 * ext4 stores the verity descriptor beginning on the next filesystem block
165 * boundary after the Merkle tree. Then, the descriptor size is stored in the
166 * last 4 bytes of the last allocated filesystem block --- which is either the
167 * block in which the descriptor ends, or the next block after that if there
168 * weren't at least 4 bytes remaining.
169 *
170 * We can't simply store the descriptor in an xattr because it *must* be
171 * encrypted when ext4 encryption is used, but ext4 encryption doesn't encrypt
172 * xattrs. Also, if the descriptor includes a large signature blob it may be
173 * too large to store in an xattr without the EA_INODE feature.
174 */
175static int ext4_write_verity_descriptor(struct inode *inode, const void *desc,
176 size_t desc_size, u64 merkle_tree_size)
177{
178 const u64 desc_pos = round_up(ext4_verity_metadata_pos(inode) +
179 merkle_tree_size, i_blocksize(inode));
180 const u64 desc_end = desc_pos + desc_size;
181 const __le32 desc_size_disk = cpu_to_le32(desc_size);
182 const u64 desc_size_pos = round_up(desc_end + sizeof(desc_size_disk),
183 i_blocksize(inode)) -
184 sizeof(desc_size_disk);
185 int err;
186
187 err = pagecache_write(inode, desc, desc_size, desc_pos);
188 if (err)
189 return err;
190
191 return pagecache_write(inode, &desc_size_disk, sizeof(desc_size_disk),
192 desc_size_pos);
193}
194
195static int ext4_end_enable_verity(struct file *filp, const void *desc,
196 size_t desc_size, u64 merkle_tree_size)
197{
198 struct inode *inode = file_inode(filp);
199 const int credits = 2; /* superblock and inode for ext4_orphan_del() */
200 handle_t *handle;
201 int err = 0;
202 int err2;
203
204 if (desc != NULL) {
205 /* Succeeded; write the verity descriptor. */
206 err = ext4_write_verity_descriptor(inode, desc, desc_size,
207 merkle_tree_size);
208
209 /* Write all pages before clearing VERITY_IN_PROGRESS. */
210 if (!err)
211 err = filemap_write_and_wait(inode->i_mapping);
212 }
213
214 /* If we failed, truncate anything we wrote past i_size. */
215 if (desc == NULL || err)
216 ext4_truncate(inode);
217
218 /*
219 * We must always clean up by clearing EXT4_STATE_VERITY_IN_PROGRESS and
220 * deleting the inode from the orphan list, even if something failed.
221 * If everything succeeded, we'll also set the verity bit in the same
222 * transaction.
223 */
224
225 ext4_clear_inode_state(inode, EXT4_STATE_VERITY_IN_PROGRESS);
226
227 handle = ext4_journal_start(inode, EXT4_HT_INODE, credits);
228 if (IS_ERR(handle)) {
229 ext4_orphan_del(NULL, inode);
230 return PTR_ERR(handle);
231 }
232
233 err2 = ext4_orphan_del(handle, inode);
234 if (err2)
235 goto out_stop;
236
237 if (desc != NULL && !err) {
238 struct ext4_iloc iloc;
239
240 err = ext4_reserve_inode_write(handle, inode, &iloc);
241 if (err)
242 goto out_stop;
243 ext4_set_inode_flag(inode, EXT4_INODE_VERITY);
244 ext4_set_inode_flags(inode);
245 err = ext4_mark_iloc_dirty(handle, inode, &iloc);
246 }
247out_stop:
248 ext4_journal_stop(handle);
249 return err ?: err2;
250}
251
252static int ext4_get_verity_descriptor_location(struct inode *inode,
253 size_t *desc_size_ret,
254 u64 *desc_pos_ret)
255{
256 struct ext4_ext_path *path;
257 struct ext4_extent *last_extent;
258 u32 end_lblk;
259 u64 desc_size_pos;
260 __le32 desc_size_disk;
261 u32 desc_size;
262 u64 desc_pos;
263 int err;
264
265 /*
266 * Descriptor size is in last 4 bytes of last allocated block.
267 * See ext4_write_verity_descriptor().
268 */
269
270 if (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)) {
271 EXT4_ERROR_INODE(inode, "verity file doesn't use extents");
272 return -EFSCORRUPTED;
273 }
274
275 path = ext4_find_extent(inode, EXT_MAX_BLOCKS - 1, NULL, 0);
276 if (IS_ERR(path))
277 return PTR_ERR(path);
278
279 last_extent = path[path->p_depth].p_ext;
280 if (!last_extent) {
281 EXT4_ERROR_INODE(inode, "verity file has no extents");
282 ext4_ext_drop_refs(path);
283 kfree(path);
284 return -EFSCORRUPTED;
285 }
286
287 end_lblk = le32_to_cpu(last_extent->ee_block) +
288 ext4_ext_get_actual_len(last_extent);
289 desc_size_pos = (u64)end_lblk << inode->i_blkbits;
290 ext4_ext_drop_refs(path);
291 kfree(path);
292
293 if (desc_size_pos < sizeof(desc_size_disk))
294 goto bad;
295 desc_size_pos -= sizeof(desc_size_disk);
296
297 err = pagecache_read(inode, &desc_size_disk, sizeof(desc_size_disk),
298 desc_size_pos);
299 if (err)
300 return err;
301 desc_size = le32_to_cpu(desc_size_disk);
302
303 /*
304 * The descriptor is stored just before the desc_size_disk, but starting
305 * on a filesystem block boundary.
306 */
307
308 if (desc_size > INT_MAX || desc_size > desc_size_pos)
309 goto bad;
310
311 desc_pos = round_down(desc_size_pos - desc_size, i_blocksize(inode));
312 if (desc_pos < ext4_verity_metadata_pos(inode))
313 goto bad;
314
315 *desc_size_ret = desc_size;
316 *desc_pos_ret = desc_pos;
317 return 0;
318
319bad:
320 EXT4_ERROR_INODE(inode, "verity file corrupted; can't find descriptor");
321 return -EFSCORRUPTED;
322}
323
324static int ext4_get_verity_descriptor(struct inode *inode, void *buf,
325 size_t buf_size)
326{
327 size_t desc_size = 0;
328 u64 desc_pos = 0;
329 int err;
330
331 err = ext4_get_verity_descriptor_location(inode, &desc_size, &desc_pos);
332 if (err)
333 return err;
334
335 if (buf_size) {
336 if (desc_size > buf_size)
337 return -ERANGE;
338 err = pagecache_read(inode, buf, desc_size, desc_pos);
339 if (err)
340 return err;
341 }
342 return desc_size;
343}
344
345static struct page *ext4_read_merkle_tree_page(struct inode *inode,
346 pgoff_t index)
347{
348 index += ext4_verity_metadata_pos(inode) >> PAGE_SHIFT;
349
350 return read_mapping_page(inode->i_mapping, index, NULL);
351}
352
353static int ext4_write_merkle_tree_block(struct inode *inode, const void *buf,
354 u64 index, int log_blocksize)
355{
356 loff_t pos = ext4_verity_metadata_pos(inode) + (index << log_blocksize);
357
358 return pagecache_write(inode, buf, 1 << log_blocksize, pos);
359}
360
361const struct fsverity_operations ext4_verityops = {
362 .begin_enable_verity = ext4_begin_enable_verity,
363 .end_enable_verity = ext4_end_enable_verity,
364 .get_verity_descriptor = ext4_get_verity_descriptor,
365 .read_merkle_tree_page = ext4_read_merkle_tree_page,
366 .write_merkle_tree_block = ext4_write_merkle_tree_block,
367};