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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/f2fs/verity.c: fs-verity support for f2fs
4 *
5 * Copyright 2019 Google LLC
6 */
7
8/*
9 * Implementation of fsverity_operations for f2fs.
10 *
11 * Like ext4, f2fs stores the verity metadata (Merkle tree and
12 * fsverity_descriptor) past the end of the file, starting at the first 64K
13 * boundary beyond i_size. This approach works because (a) verity files are
14 * readonly, and (b) pages fully beyond i_size aren't visible to userspace but
15 * can be read/written internally by f2fs with only some relatively small
16 * changes to f2fs. Extended attributes cannot be used because (a) f2fs limits
17 * the total size of an inode's xattr entries to 4096 bytes, which wouldn't be
18 * enough for even a single Merkle tree block, and (b) f2fs encryption doesn't
19 * encrypt xattrs, yet the verity metadata *must* be encrypted when the file is
20 * because it contains hashes of the plaintext data.
21 *
22 * Using a 64K boundary rather than a 4K one keeps things ready for
23 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
24 * since there can be a hole between i_size and the start of the Merkle tree.
25 */
26
27#include <linux/f2fs_fs.h>
28
29#include "f2fs.h"
30#include "xattr.h"
31
32static inline loff_t f2fs_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
109/*
110 * Format of f2fs verity xattr. This points to the location of the verity
111 * descriptor within the file data rather than containing it directly because
112 * the verity descriptor *must* be encrypted when f2fs encryption is used. But,
113 * f2fs encryption does not encrypt xattrs.
114 */
115struct fsverity_descriptor_location {
116 __le32 version;
117 __le32 size;
118 __le64 pos;
119};
120
121static int f2fs_begin_enable_verity(struct file *filp)
122{
123 struct inode *inode = file_inode(filp);
124 int err;
125
126 if (f2fs_verity_in_progress(inode))
127 return -EBUSY;
128
129 if (f2fs_is_atomic_file(inode) || f2fs_is_volatile_file(inode))
130 return -EOPNOTSUPP;
131
132 /*
133 * Since the file was opened readonly, we have to initialize the quotas
134 * here and not rely on ->open() doing it. This must be done before
135 * evicting the inline data.
136 */
137 err = dquot_initialize(inode);
138 if (err)
139 return err;
140
141 err = f2fs_convert_inline_inode(inode);
142 if (err)
143 return err;
144
145 set_inode_flag(inode, FI_VERITY_IN_PROGRESS);
146 return 0;
147}
148
149static int f2fs_end_enable_verity(struct file *filp, const void *desc,
150 size_t desc_size, u64 merkle_tree_size)
151{
152 struct inode *inode = file_inode(filp);
153 u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
154 struct fsverity_descriptor_location dloc = {
155 .version = cpu_to_le32(1),
156 .size = cpu_to_le32(desc_size),
157 .pos = cpu_to_le64(desc_pos),
158 };
159 int err = 0;
160
161 if (desc != NULL) {
162 /* Succeeded; write the verity descriptor. */
163 err = pagecache_write(inode, desc, desc_size, desc_pos);
164
165 /* Write all pages before clearing FI_VERITY_IN_PROGRESS. */
166 if (!err)
167 err = filemap_write_and_wait(inode->i_mapping);
168 }
169
170 /* If we failed, truncate anything we wrote past i_size. */
171 if (desc == NULL || err)
172 f2fs_truncate(inode);
173
174 clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
175
176 if (desc != NULL && !err) {
177 err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
178 F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
179 NULL, XATTR_CREATE);
180 if (!err) {
181 file_set_verity(inode);
182 f2fs_set_inode_flags(inode);
183 f2fs_mark_inode_dirty_sync(inode, true);
184 }
185 }
186 return err;
187}
188
189static int f2fs_get_verity_descriptor(struct inode *inode, void *buf,
190 size_t buf_size)
191{
192 struct fsverity_descriptor_location dloc;
193 int res;
194 u32 size;
195 u64 pos;
196
197 /* Get the descriptor location */
198 res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY,
199 F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL);
200 if (res < 0 && res != -ERANGE)
201 return res;
202 if (res != sizeof(dloc) || dloc.version != cpu_to_le32(1)) {
203 f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format");
204 return -EINVAL;
205 }
206 size = le32_to_cpu(dloc.size);
207 pos = le64_to_cpu(dloc.pos);
208
209 /* Get the descriptor */
210 if (pos + size < pos || pos + size > inode->i_sb->s_maxbytes ||
211 pos < f2fs_verity_metadata_pos(inode) || size > INT_MAX) {
212 f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr");
213 return -EFSCORRUPTED;
214 }
215 if (buf_size) {
216 if (size > buf_size)
217 return -ERANGE;
218 res = pagecache_read(inode, buf, size, pos);
219 if (res)
220 return res;
221 }
222 return size;
223}
224
225static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
226 pgoff_t index)
227{
228 index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;
229
230 return read_mapping_page(inode->i_mapping, index, NULL);
231}
232
233static int f2fs_write_merkle_tree_block(struct inode *inode, const void *buf,
234 u64 index, int log_blocksize)
235{
236 loff_t pos = f2fs_verity_metadata_pos(inode) + (index << log_blocksize);
237
238 return pagecache_write(inode, buf, 1 << log_blocksize, pos);
239}
240
241const struct fsverity_operations f2fs_verityops = {
242 .begin_enable_verity = f2fs_begin_enable_verity,
243 .end_enable_verity = f2fs_end_enable_verity,
244 .get_verity_descriptor = f2fs_get_verity_descriptor,
245 .read_merkle_tree_page = f2fs_read_merkle_tree_page,
246 .write_merkle_tree_block = f2fs_write_merkle_tree_block,
247};
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * fs/f2fs/verity.c: fs-verity support for f2fs
4 *
5 * Copyright 2019 Google LLC
6 */
7
8/*
9 * Implementation of fsverity_operations for f2fs.
10 *
11 * Like ext4, f2fs stores the verity metadata (Merkle tree and
12 * fsverity_descriptor) past the end of the file, starting at the first 64K
13 * boundary beyond i_size. This approach works because (a) verity files are
14 * readonly, and (b) pages fully beyond i_size aren't visible to userspace but
15 * can be read/written internally by f2fs with only some relatively small
16 * changes to f2fs. Extended attributes cannot be used because (a) f2fs limits
17 * the total size of an inode's xattr entries to 4096 bytes, which wouldn't be
18 * enough for even a single Merkle tree block, and (b) f2fs encryption doesn't
19 * encrypt xattrs, yet the verity metadata *must* be encrypted when the file is
20 * because it contains hashes of the plaintext data.
21 *
22 * Using a 64K boundary rather than a 4K one keeps things ready for
23 * architectures with 64K pages, and it doesn't necessarily waste space on-disk
24 * since there can be a hole between i_size and the start of the Merkle tree.
25 */
26
27#include <linux/f2fs_fs.h>
28
29#include "f2fs.h"
30#include "xattr.h"
31
32#define F2FS_VERIFY_VER (1)
33
34static inline loff_t f2fs_verity_metadata_pos(const struct inode *inode)
35{
36 return round_up(inode->i_size, 65536);
37}
38
39/*
40 * Read some verity metadata from the inode. __vfs_read() can't be used because
41 * we need to read beyond i_size.
42 */
43static int pagecache_read(struct inode *inode, void *buf, size_t count,
44 loff_t pos)
45{
46 while (count) {
47 size_t n = min_t(size_t, count,
48 PAGE_SIZE - offset_in_page(pos));
49 struct page *page;
50
51 page = read_mapping_page(inode->i_mapping, pos >> PAGE_SHIFT,
52 NULL);
53 if (IS_ERR(page))
54 return PTR_ERR(page);
55
56 memcpy_from_page(buf, page, offset_in_page(pos), n);
57
58 put_page(page);
59
60 buf += n;
61 pos += n;
62 count -= n;
63 }
64 return 0;
65}
66
67/*
68 * Write some verity metadata to the inode for FS_IOC_ENABLE_VERITY.
69 * kernel_write() can't be used because the file descriptor is readonly.
70 */
71static int pagecache_write(struct inode *inode, const void *buf, size_t count,
72 loff_t pos)
73{
74 struct address_space *mapping = inode->i_mapping;
75 const struct address_space_operations *aops = mapping->a_ops;
76
77 if (pos + count > F2FS_BLK_TO_BYTES(max_file_blocks(inode)))
78 return -EFBIG;
79
80 while (count) {
81 size_t n = min_t(size_t, count,
82 PAGE_SIZE - offset_in_page(pos));
83 struct folio *folio;
84 void *fsdata = NULL;
85 int res;
86
87 res = aops->write_begin(NULL, mapping, pos, n, &folio, &fsdata);
88 if (res)
89 return res;
90
91 memcpy_to_folio(folio, offset_in_folio(folio, pos), buf, n);
92
93 res = aops->write_end(NULL, mapping, pos, n, n, folio, fsdata);
94 if (res < 0)
95 return res;
96 if (res != n)
97 return -EIO;
98
99 buf += n;
100 pos += n;
101 count -= n;
102 }
103 return 0;
104}
105
106/*
107 * Format of f2fs verity xattr. This points to the location of the verity
108 * descriptor within the file data rather than containing it directly because
109 * the verity descriptor *must* be encrypted when f2fs encryption is used. But,
110 * f2fs encryption does not encrypt xattrs.
111 */
112struct fsverity_descriptor_location {
113 __le32 version;
114 __le32 size;
115 __le64 pos;
116};
117
118static int f2fs_begin_enable_verity(struct file *filp)
119{
120 struct inode *inode = file_inode(filp);
121 int err;
122
123 if (f2fs_verity_in_progress(inode))
124 return -EBUSY;
125
126 if (f2fs_is_atomic_file(inode))
127 return -EOPNOTSUPP;
128
129 /*
130 * Since the file was opened readonly, we have to initialize the quotas
131 * here and not rely on ->open() doing it. This must be done before
132 * evicting the inline data.
133 */
134 err = f2fs_dquot_initialize(inode);
135 if (err)
136 return err;
137
138 err = f2fs_convert_inline_inode(inode);
139 if (err)
140 return err;
141
142 set_inode_flag(inode, FI_VERITY_IN_PROGRESS);
143 return 0;
144}
145
146static int f2fs_end_enable_verity(struct file *filp, const void *desc,
147 size_t desc_size, u64 merkle_tree_size)
148{
149 struct inode *inode = file_inode(filp);
150 struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
151 u64 desc_pos = f2fs_verity_metadata_pos(inode) + merkle_tree_size;
152 struct fsverity_descriptor_location dloc = {
153 .version = cpu_to_le32(F2FS_VERIFY_VER),
154 .size = cpu_to_le32(desc_size),
155 .pos = cpu_to_le64(desc_pos),
156 };
157 int err = 0, err2 = 0;
158
159 /*
160 * If an error already occurred (which fs/verity/ signals by passing
161 * desc == NULL), then only clean-up is needed.
162 */
163 if (desc == NULL)
164 goto cleanup;
165
166 /* Append the verity descriptor. */
167 err = pagecache_write(inode, desc, desc_size, desc_pos);
168 if (err)
169 goto cleanup;
170
171 /*
172 * Write all pages (both data and verity metadata). Note that this must
173 * happen before clearing FI_VERITY_IN_PROGRESS; otherwise pages beyond
174 * i_size won't be written properly. For crash consistency, this also
175 * must happen before the verity inode flag gets persisted.
176 */
177 err = filemap_write_and_wait(inode->i_mapping);
178 if (err)
179 goto cleanup;
180
181 /* Set the verity xattr. */
182 err = f2fs_setxattr(inode, F2FS_XATTR_INDEX_VERITY,
183 F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc),
184 NULL, XATTR_CREATE);
185 if (err)
186 goto cleanup;
187
188 /* Finally, set the verity inode flag. */
189 file_set_verity(inode);
190 f2fs_set_inode_flags(inode);
191 f2fs_mark_inode_dirty_sync(inode, true);
192
193 clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
194 return 0;
195
196cleanup:
197 /*
198 * Verity failed to be enabled, so clean up by truncating any verity
199 * metadata that was written beyond i_size (both from cache and from
200 * disk) and clearing FI_VERITY_IN_PROGRESS.
201 *
202 * Taking i_gc_rwsem[WRITE] is needed to stop f2fs garbage collection
203 * from re-instantiating cached pages we are truncating (since unlike
204 * normal file accesses, garbage collection isn't limited by i_size).
205 */
206 f2fs_down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
207 truncate_inode_pages(inode->i_mapping, inode->i_size);
208 err2 = f2fs_truncate(inode);
209 if (err2) {
210 f2fs_err(sbi, "Truncating verity metadata failed (errno=%d)",
211 err2);
212 set_sbi_flag(sbi, SBI_NEED_FSCK);
213 }
214 f2fs_up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
215 clear_inode_flag(inode, FI_VERITY_IN_PROGRESS);
216 return err ?: err2;
217}
218
219static int f2fs_get_verity_descriptor(struct inode *inode, void *buf,
220 size_t buf_size)
221{
222 struct fsverity_descriptor_location dloc;
223 int res;
224 u32 size;
225 u64 pos;
226
227 /* Get the descriptor location */
228 res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_VERITY,
229 F2FS_XATTR_NAME_VERITY, &dloc, sizeof(dloc), NULL);
230 if (res < 0 && res != -ERANGE)
231 return res;
232 if (res != sizeof(dloc) || dloc.version != cpu_to_le32(F2FS_VERIFY_VER)) {
233 f2fs_warn(F2FS_I_SB(inode), "unknown verity xattr format");
234 return -EINVAL;
235 }
236 size = le32_to_cpu(dloc.size);
237 pos = le64_to_cpu(dloc.pos);
238
239 /* Get the descriptor */
240 if (pos + size < pos ||
241 pos + size > F2FS_BLK_TO_BYTES(max_file_blocks(inode)) ||
242 pos < f2fs_verity_metadata_pos(inode) || size > INT_MAX) {
243 f2fs_warn(F2FS_I_SB(inode), "invalid verity xattr");
244 f2fs_handle_error(F2FS_I_SB(inode),
245 ERROR_CORRUPTED_VERITY_XATTR);
246 return -EFSCORRUPTED;
247 }
248 if (buf_size) {
249 if (size > buf_size)
250 return -ERANGE;
251 res = pagecache_read(inode, buf, size, pos);
252 if (res)
253 return res;
254 }
255 return size;
256}
257
258static struct page *f2fs_read_merkle_tree_page(struct inode *inode,
259 pgoff_t index,
260 unsigned long num_ra_pages)
261{
262 struct folio *folio;
263
264 index += f2fs_verity_metadata_pos(inode) >> PAGE_SHIFT;
265
266 folio = __filemap_get_folio(inode->i_mapping, index, FGP_ACCESSED, 0);
267 if (IS_ERR(folio) || !folio_test_uptodate(folio)) {
268 DEFINE_READAHEAD(ractl, NULL, NULL, inode->i_mapping, index);
269
270 if (!IS_ERR(folio))
271 folio_put(folio);
272 else if (num_ra_pages > 1)
273 page_cache_ra_unbounded(&ractl, num_ra_pages, 0);
274 folio = read_mapping_folio(inode->i_mapping, index, NULL);
275 if (IS_ERR(folio))
276 return ERR_CAST(folio);
277 }
278 return folio_file_page(folio, index);
279}
280
281static int f2fs_write_merkle_tree_block(struct inode *inode, const void *buf,
282 u64 pos, unsigned int size)
283{
284 pos += f2fs_verity_metadata_pos(inode);
285
286 return pagecache_write(inode, buf, size, pos);
287}
288
289const struct fsverity_operations f2fs_verityops = {
290 .begin_enable_verity = f2fs_begin_enable_verity,
291 .end_enable_verity = f2fs_end_enable_verity,
292 .get_verity_descriptor = f2fs_get_verity_descriptor,
293 .read_merkle_tree_page = f2fs_read_merkle_tree_page,
294 .write_merkle_tree_block = f2fs_write_merkle_tree_block,
295};