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5fee3609 ST |
1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* | |
3 | * Inline encryption support for fscrypt | |
4 | * | |
5 | * Copyright 2019 Google LLC | |
6 | */ | |
7 | ||
8 | /* | |
9 | * With "inline encryption", the block layer handles the decryption/encryption | |
10 | * as part of the bio, instead of the filesystem doing the crypto itself via | |
11 | * crypto API. See Documentation/block/inline-encryption.rst. fscrypt still | |
12 | * provides the key and IV to use. | |
13 | */ | |
14 | ||
6715c98b | 15 | #include <linux/blk-crypto.h> |
5fee3609 ST |
16 | #include <linux/blkdev.h> |
17 | #include <linux/buffer_head.h> | |
18 | #include <linux/sched/mm.h> | |
453431a5 | 19 | #include <linux/slab.h> |
c6c89783 | 20 | #include <linux/uio.h> |
5fee3609 ST |
21 | |
22 | #include "fscrypt_private.h" | |
23 | ||
0e91fc1e CH |
24 | static struct block_device **fscrypt_get_devices(struct super_block *sb, |
25 | unsigned int *num_devs) | |
5fee3609 | 26 | { |
0e91fc1e | 27 | struct block_device **devs; |
5fee3609 | 28 | |
0e91fc1e CH |
29 | if (sb->s_cop->get_devices) { |
30 | devs = sb->s_cop->get_devices(sb, num_devs); | |
31 | if (devs) | |
32 | return devs; | |
33 | } | |
34 | devs = kmalloc(sizeof(*devs), GFP_KERNEL); | |
35 | if (!devs) | |
36 | return ERR_PTR(-ENOMEM); | |
37 | devs[0] = sb->s_bdev; | |
38 | *num_devs = 1; | |
39 | return devs; | |
5fee3609 ST |
40 | } |
41 | ||
3e7807d5 | 42 | static unsigned int fscrypt_get_dun_bytes(const struct fscrypt_inode_info *ci) |
5fee3609 | 43 | { |
f0904e8b | 44 | const struct super_block *sb = ci->ci_inode->i_sb; |
5fee3609 | 45 | unsigned int flags = fscrypt_policy_flags(&ci->ci_policy); |
5b118884 | 46 | int dun_bits; |
5fee3609 ST |
47 | |
48 | if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) | |
49 | return offsetofend(union fscrypt_iv, nonce); | |
50 | ||
51 | if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) | |
52 | return sizeof(__le64); | |
53 | ||
54 | if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) | |
55 | return sizeof(__le32); | |
56 | ||
5b118884 EB |
57 | /* Default case: IVs are just the file data unit index */ |
58 | dun_bits = fscrypt_max_file_dun_bits(sb, ci->ci_data_unit_bits); | |
59 | return DIV_ROUND_UP(dun_bits, 8); | |
5fee3609 ST |
60 | } |
61 | ||
a7a5bc5f EB |
62 | /* |
63 | * Log a message when starting to use blk-crypto (native) or blk-crypto-fallback | |
64 | * for an encryption mode for the first time. This is the blk-crypto | |
65 | * counterpart to the message logged when starting to use the crypto API for the | |
66 | * first time. A limitation is that these messages don't convey which specific | |
67 | * filesystems or files are using each implementation. However, *usually* | |
68 | * systems use just one implementation per mode, which makes these messages | |
69 | * helpful for debugging problems where the "wrong" implementation is used. | |
70 | */ | |
71 | static void fscrypt_log_blk_crypto_impl(struct fscrypt_mode *mode, | |
0e91fc1e CH |
72 | struct block_device **devs, |
73 | unsigned int num_devs, | |
a7a5bc5f EB |
74 | const struct blk_crypto_config *cfg) |
75 | { | |
0e91fc1e | 76 | unsigned int i; |
a7a5bc5f EB |
77 | |
78 | for (i = 0; i < num_devs; i++) { | |
79 | if (!IS_ENABLED(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) || | |
6715c98b | 80 | blk_crypto_config_supported_natively(devs[i], cfg)) { |
a7a5bc5f EB |
81 | if (!xchg(&mode->logged_blk_crypto_native, 1)) |
82 | pr_info("fscrypt: %s using blk-crypto (native)\n", | |
83 | mode->friendly_name); | |
84 | } else if (!xchg(&mode->logged_blk_crypto_fallback, 1)) { | |
85 | pr_info("fscrypt: %s using blk-crypto-fallback\n", | |
86 | mode->friendly_name); | |
87 | } | |
88 | } | |
89 | } | |
90 | ||
5fee3609 | 91 | /* Enable inline encryption for this file if supported. */ |
3e7807d5 | 92 | int fscrypt_select_encryption_impl(struct fscrypt_inode_info *ci) |
5fee3609 ST |
93 | { |
94 | const struct inode *inode = ci->ci_inode; | |
95 | struct super_block *sb = inode->i_sb; | |
96 | struct blk_crypto_config crypto_cfg; | |
0e91fc1e CH |
97 | struct block_device **devs; |
98 | unsigned int num_devs; | |
99 | unsigned int i; | |
5fee3609 ST |
100 | |
101 | /* The file must need contents encryption, not filenames encryption */ | |
d19d8d34 | 102 | if (!S_ISREG(inode->i_mode)) |
5fee3609 ST |
103 | return 0; |
104 | ||
105 | /* The crypto mode must have a blk-crypto counterpart */ | |
106 | if (ci->ci_mode->blk_crypto_mode == BLK_ENCRYPTION_MODE_INVALID) | |
107 | return 0; | |
108 | ||
109 | /* The filesystem must be mounted with -o inlinecrypt */ | |
110 | if (!(sb->s_flags & SB_INLINECRYPT)) | |
111 | return 0; | |
112 | ||
113 | /* | |
114 | * When a page contains multiple logically contiguous filesystem blocks, | |
115 | * some filesystem code only calls fscrypt_mergeable_bio() for the first | |
116 | * block in the page. This is fine for most of fscrypt's IV generation | |
117 | * strategies, where contiguous blocks imply contiguous IVs. But it | |
118 | * doesn't work with IV_INO_LBLK_32. For now, simply exclude | |
119 | * IV_INO_LBLK_32 with blocksize != PAGE_SIZE from inline encryption. | |
120 | */ | |
121 | if ((fscrypt_policy_flags(&ci->ci_policy) & | |
122 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) && | |
123 | sb->s_blocksize != PAGE_SIZE) | |
124 | return 0; | |
125 | ||
126 | /* | |
0e91fc1e CH |
127 | * On all the filesystem's block devices, blk-crypto must support the |
128 | * crypto configuration that the file would use. | |
5fee3609 ST |
129 | */ |
130 | crypto_cfg.crypto_mode = ci->ci_mode->blk_crypto_mode; | |
5b118884 | 131 | crypto_cfg.data_unit_size = 1U << ci->ci_data_unit_bits; |
5fee3609 | 132 | crypto_cfg.dun_bytes = fscrypt_get_dun_bytes(ci); |
0e91fc1e CH |
133 | |
134 | devs = fscrypt_get_devices(sb, &num_devs); | |
135 | if (IS_ERR(devs)) | |
136 | return PTR_ERR(devs); | |
5fee3609 ST |
137 | |
138 | for (i = 0; i < num_devs; i++) { | |
fce3caea | 139 | if (!blk_crypto_config_supported(devs[i], &crypto_cfg)) |
5fee3609 ST |
140 | goto out_free_devs; |
141 | } | |
142 | ||
a7a5bc5f EB |
143 | fscrypt_log_blk_crypto_impl(ci->ci_mode, devs, num_devs, &crypto_cfg); |
144 | ||
5fee3609 ST |
145 | ci->ci_inlinecrypt = true; |
146 | out_free_devs: | |
147 | kfree(devs); | |
148 | ||
149 | return 0; | |
150 | } | |
151 | ||
152 | int fscrypt_prepare_inline_crypt_key(struct fscrypt_prepared_key *prep_key, | |
153 | const u8 *raw_key, | |
3e7807d5 | 154 | const struct fscrypt_inode_info *ci) |
5fee3609 ST |
155 | { |
156 | const struct inode *inode = ci->ci_inode; | |
157 | struct super_block *sb = inode->i_sb; | |
158 | enum blk_crypto_mode_num crypto_mode = ci->ci_mode->blk_crypto_mode; | |
22e9947a | 159 | struct blk_crypto_key *blk_key; |
0e91fc1e | 160 | struct block_device **devs; |
22e9947a EB |
161 | unsigned int num_devs; |
162 | unsigned int i; | |
5fee3609 | 163 | int err; |
5fee3609 | 164 | |
22e9947a | 165 | blk_key = kmalloc(sizeof(*blk_key), GFP_KERNEL); |
5fee3609 ST |
166 | if (!blk_key) |
167 | return -ENOMEM; | |
168 | ||
22e9947a | 169 | err = blk_crypto_init_key(blk_key, raw_key, crypto_mode, |
5b118884 EB |
170 | fscrypt_get_dun_bytes(ci), |
171 | 1U << ci->ci_data_unit_bits); | |
5fee3609 ST |
172 | if (err) { |
173 | fscrypt_err(inode, "error %d initializing blk-crypto key", err); | |
174 | goto fail; | |
175 | } | |
176 | ||
22e9947a | 177 | /* Start using blk-crypto on all the filesystem's block devices. */ |
0e91fc1e CH |
178 | devs = fscrypt_get_devices(sb, &num_devs); |
179 | if (IS_ERR(devs)) { | |
180 | err = PTR_ERR(devs); | |
22e9947a EB |
181 | goto fail; |
182 | } | |
5fee3609 | 183 | for (i = 0; i < num_devs; i++) { |
fce3caea | 184 | err = blk_crypto_start_using_key(devs[i], blk_key); |
22e9947a EB |
185 | if (err) |
186 | break; | |
5fee3609 | 187 | } |
22e9947a EB |
188 | kfree(devs); |
189 | if (err) { | |
190 | fscrypt_err(inode, "error %d starting to use blk-crypto", err); | |
191 | goto fail; | |
192 | } | |
193 | ||
5fee3609 | 194 | /* |
97c6327f EB |
195 | * Pairs with the smp_load_acquire() in fscrypt_is_key_prepared(). |
196 | * I.e., here we publish ->blk_key with a RELEASE barrier so that | |
197 | * concurrent tasks can ACQUIRE it. Note that this concurrency is only | |
198 | * possible for per-mode keys, not for per-file keys. | |
5fee3609 ST |
199 | */ |
200 | smp_store_release(&prep_key->blk_key, blk_key); | |
201 | return 0; | |
202 | ||
203 | fail: | |
453431a5 | 204 | kfree_sensitive(blk_key); |
5fee3609 ST |
205 | return err; |
206 | } | |
207 | ||
22e9947a EB |
208 | void fscrypt_destroy_inline_crypt_key(struct super_block *sb, |
209 | struct fscrypt_prepared_key *prep_key) | |
5fee3609 | 210 | { |
22e9947a | 211 | struct blk_crypto_key *blk_key = prep_key->blk_key; |
0e91fc1e | 212 | struct block_device **devs; |
22e9947a EB |
213 | unsigned int num_devs; |
214 | unsigned int i; | |
5fee3609 | 215 | |
22e9947a EB |
216 | if (!blk_key) |
217 | return; | |
218 | ||
219 | /* Evict the key from all the filesystem's block devices. */ | |
0e91fc1e CH |
220 | devs = fscrypt_get_devices(sb, &num_devs); |
221 | if (!IS_ERR(devs)) { | |
22e9947a | 222 | for (i = 0; i < num_devs; i++) |
fce3caea | 223 | blk_crypto_evict_key(devs[i], blk_key); |
22e9947a | 224 | kfree(devs); |
5fee3609 | 225 | } |
22e9947a | 226 | kfree_sensitive(blk_key); |
5fee3609 ST |
227 | } |
228 | ||
229 | bool __fscrypt_inode_uses_inline_crypto(const struct inode *inode) | |
230 | { | |
231 | return inode->i_crypt_info->ci_inlinecrypt; | |
232 | } | |
233 | EXPORT_SYMBOL_GPL(__fscrypt_inode_uses_inline_crypto); | |
234 | ||
3e7807d5 JB |
235 | static void fscrypt_generate_dun(const struct fscrypt_inode_info *ci, |
236 | u64 lblk_num, | |
5fee3609 ST |
237 | u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]) |
238 | { | |
5b118884 | 239 | u64 index = lblk_num << ci->ci_data_units_per_block_bits; |
5fee3609 ST |
240 | union fscrypt_iv iv; |
241 | int i; | |
242 | ||
5b118884 | 243 | fscrypt_generate_iv(&iv, index, ci); |
5fee3609 ST |
244 | |
245 | BUILD_BUG_ON(FSCRYPT_MAX_IV_SIZE > BLK_CRYPTO_MAX_IV_SIZE); | |
246 | memset(dun, 0, BLK_CRYPTO_MAX_IV_SIZE); | |
247 | for (i = 0; i < ci->ci_mode->ivsize/sizeof(dun[0]); i++) | |
248 | dun[i] = le64_to_cpu(iv.dun[i]); | |
249 | } | |
250 | ||
251 | /** | |
252 | * fscrypt_set_bio_crypt_ctx() - prepare a file contents bio for inline crypto | |
253 | * @bio: a bio which will eventually be submitted to the file | |
254 | * @inode: the file's inode | |
255 | * @first_lblk: the first file logical block number in the I/O | |
256 | * @gfp_mask: memory allocation flags - these must be a waiting mask so that | |
257 | * bio_crypt_set_ctx can't fail. | |
258 | * | |
259 | * If the contents of the file should be encrypted (or decrypted) with inline | |
260 | * encryption, then assign the appropriate encryption context to the bio. | |
261 | * | |
262 | * Normally the bio should be newly allocated (i.e. no pages added yet), as | |
263 | * otherwise fscrypt_mergeable_bio() won't work as intended. | |
264 | * | |
265 | * The encryption context will be freed automatically when the bio is freed. | |
266 | */ | |
267 | void fscrypt_set_bio_crypt_ctx(struct bio *bio, const struct inode *inode, | |
268 | u64 first_lblk, gfp_t gfp_mask) | |
269 | { | |
3e7807d5 | 270 | const struct fscrypt_inode_info *ci; |
5fee3609 ST |
271 | u64 dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; |
272 | ||
273 | if (!fscrypt_inode_uses_inline_crypto(inode)) | |
274 | return; | |
55e32c54 | 275 | ci = inode->i_crypt_info; |
5fee3609 ST |
276 | |
277 | fscrypt_generate_dun(ci, first_lblk, dun); | |
22e9947a | 278 | bio_crypt_set_ctx(bio, ci->ci_enc_key.blk_key, dun, gfp_mask); |
5fee3609 ST |
279 | } |
280 | EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx); | |
281 | ||
282 | /* Extract the inode and logical block number from a buffer_head. */ | |
283 | static bool bh_get_inode_and_lblk_num(const struct buffer_head *bh, | |
284 | const struct inode **inode_ret, | |
285 | u64 *lblk_num_ret) | |
286 | { | |
287 | struct page *page = bh->b_page; | |
288 | const struct address_space *mapping; | |
289 | const struct inode *inode; | |
290 | ||
291 | /* | |
292 | * The ext4 journal (jbd2) can submit a buffer_head it directly created | |
293 | * for a non-pagecache page. fscrypt doesn't care about these. | |
294 | */ | |
295 | mapping = page_mapping(page); | |
296 | if (!mapping) | |
297 | return false; | |
298 | inode = mapping->host; | |
299 | ||
300 | *inode_ret = inode; | |
301 | *lblk_num_ret = ((u64)page->index << (PAGE_SHIFT - inode->i_blkbits)) + | |
302 | (bh_offset(bh) >> inode->i_blkbits); | |
303 | return true; | |
304 | } | |
305 | ||
306 | /** | |
307 | * fscrypt_set_bio_crypt_ctx_bh() - prepare a file contents bio for inline | |
308 | * crypto | |
309 | * @bio: a bio which will eventually be submitted to the file | |
310 | * @first_bh: the first buffer_head for which I/O will be submitted | |
311 | * @gfp_mask: memory allocation flags | |
312 | * | |
313 | * Same as fscrypt_set_bio_crypt_ctx(), except this takes a buffer_head instead | |
314 | * of an inode and block number directly. | |
315 | */ | |
316 | void fscrypt_set_bio_crypt_ctx_bh(struct bio *bio, | |
317 | const struct buffer_head *first_bh, | |
318 | gfp_t gfp_mask) | |
319 | { | |
320 | const struct inode *inode; | |
321 | u64 first_lblk; | |
322 | ||
323 | if (bh_get_inode_and_lblk_num(first_bh, &inode, &first_lblk)) | |
324 | fscrypt_set_bio_crypt_ctx(bio, inode, first_lblk, gfp_mask); | |
325 | } | |
326 | EXPORT_SYMBOL_GPL(fscrypt_set_bio_crypt_ctx_bh); | |
327 | ||
328 | /** | |
329 | * fscrypt_mergeable_bio() - test whether data can be added to a bio | |
330 | * @bio: the bio being built up | |
331 | * @inode: the inode for the next part of the I/O | |
332 | * @next_lblk: the next file logical block number in the I/O | |
333 | * | |
334 | * When building a bio which may contain data which should undergo inline | |
335 | * encryption (or decryption) via fscrypt, filesystems should call this function | |
336 | * to ensure that the resulting bio contains only contiguous data unit numbers. | |
337 | * This will return false if the next part of the I/O cannot be merged with the | |
338 | * bio because either the encryption key would be different or the encryption | |
339 | * data unit numbers would be discontiguous. | |
340 | * | |
341 | * fscrypt_set_bio_crypt_ctx() must have already been called on the bio. | |
342 | * | |
c6c89783 EB |
343 | * This function isn't required in cases where crypto-mergeability is ensured in |
344 | * another way, such as I/O targeting only a single file (and thus a single key) | |
345 | * combined with fscrypt_limit_io_blocks() to ensure DUN contiguity. | |
346 | * | |
5fee3609 ST |
347 | * Return: true iff the I/O is mergeable |
348 | */ | |
349 | bool fscrypt_mergeable_bio(struct bio *bio, const struct inode *inode, | |
350 | u64 next_lblk) | |
351 | { | |
352 | const struct bio_crypt_ctx *bc = bio->bi_crypt_context; | |
353 | u64 next_dun[BLK_CRYPTO_DUN_ARRAY_SIZE]; | |
354 | ||
355 | if (!!bc != fscrypt_inode_uses_inline_crypto(inode)) | |
356 | return false; | |
357 | if (!bc) | |
358 | return true; | |
359 | ||
360 | /* | |
361 | * Comparing the key pointers is good enough, as all I/O for each key | |
362 | * uses the same pointer. I.e., there's currently no need to support | |
363 | * merging requests where the keys are the same but the pointers differ. | |
364 | */ | |
22e9947a | 365 | if (bc->bc_key != inode->i_crypt_info->ci_enc_key.blk_key) |
5fee3609 ST |
366 | return false; |
367 | ||
368 | fscrypt_generate_dun(inode->i_crypt_info, next_lblk, next_dun); | |
369 | return bio_crypt_dun_is_contiguous(bc, bio->bi_iter.bi_size, next_dun); | |
370 | } | |
371 | EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio); | |
372 | ||
373 | /** | |
374 | * fscrypt_mergeable_bio_bh() - test whether data can be added to a bio | |
375 | * @bio: the bio being built up | |
376 | * @next_bh: the next buffer_head for which I/O will be submitted | |
377 | * | |
378 | * Same as fscrypt_mergeable_bio(), except this takes a buffer_head instead of | |
379 | * an inode and block number directly. | |
380 | * | |
381 | * Return: true iff the I/O is mergeable | |
382 | */ | |
383 | bool fscrypt_mergeable_bio_bh(struct bio *bio, | |
384 | const struct buffer_head *next_bh) | |
385 | { | |
386 | const struct inode *inode; | |
387 | u64 next_lblk; | |
388 | ||
389 | if (!bh_get_inode_and_lblk_num(next_bh, &inode, &next_lblk)) | |
390 | return !bio->bi_crypt_context; | |
391 | ||
392 | return fscrypt_mergeable_bio(bio, inode, next_lblk); | |
393 | } | |
394 | EXPORT_SYMBOL_GPL(fscrypt_mergeable_bio_bh); | |
c6c89783 EB |
395 | |
396 | /** | |
53dd3f80 EB |
397 | * fscrypt_dio_supported() - check whether DIO (direct I/O) is supported on an |
398 | * inode, as far as encryption is concerned | |
399 | * @inode: the inode in question | |
c6c89783 EB |
400 | * |
401 | * Return: %true if there are no encryption constraints that prevent DIO from | |
402 | * being supported; %false if DIO is unsupported. (Note that in the | |
403 | * %true case, the filesystem might have other, non-encryption-related | |
53dd3f80 EB |
404 | * constraints that prevent DIO from actually being supported. Also, on |
405 | * encrypted files the filesystem is still responsible for only allowing | |
406 | * DIO when requests are filesystem-block-aligned.) | |
c6c89783 | 407 | */ |
53dd3f80 | 408 | bool fscrypt_dio_supported(struct inode *inode) |
c6c89783 | 409 | { |
53dd3f80 | 410 | int err; |
c6c89783 EB |
411 | |
412 | /* If the file is unencrypted, no veto from us. */ | |
413 | if (!fscrypt_needs_contents_encryption(inode)) | |
414 | return true; | |
415 | ||
c6c89783 | 416 | /* |
53dd3f80 | 417 | * We only support DIO with inline crypto, not fs-layer crypto. |
c6c89783 | 418 | * |
53dd3f80 EB |
419 | * To determine whether the inode is using inline crypto, we have to set |
420 | * up the key if it wasn't already done. This is because in the current | |
421 | * design of fscrypt, the decision of whether to use inline crypto or | |
422 | * not isn't made until the inode's encryption key is being set up. In | |
423 | * the DIO read/write case, the key will always be set up already, since | |
424 | * the file will be open. But in the case of statx(), the key might not | |
425 | * be set up yet, as the file might not have been opened yet. | |
c6c89783 | 426 | */ |
53dd3f80 EB |
427 | err = fscrypt_require_key(inode); |
428 | if (err) { | |
429 | /* | |
430 | * Key unavailable or couldn't be set up. This edge case isn't | |
431 | * worth worrying about; just report that DIO is unsupported. | |
432 | */ | |
c6c89783 | 433 | return false; |
53dd3f80 EB |
434 | } |
435 | return fscrypt_inode_uses_inline_crypto(inode); | |
c6c89783 EB |
436 | } |
437 | EXPORT_SYMBOL_GPL(fscrypt_dio_supported); | |
438 | ||
439 | /** | |
440 | * fscrypt_limit_io_blocks() - limit I/O blocks to avoid discontiguous DUNs | |
441 | * @inode: the file on which I/O is being done | |
442 | * @lblk: the block at which the I/O is being started from | |
443 | * @nr_blocks: the number of blocks we want to submit starting at @lblk | |
444 | * | |
445 | * Determine the limit to the number of blocks that can be submitted in a bio | |
446 | * targeting @lblk without causing a data unit number (DUN) discontiguity. | |
447 | * | |
448 | * This is normally just @nr_blocks, as normally the DUNs just increment along | |
449 | * with the logical blocks. (Or the file is not encrypted.) | |
450 | * | |
451 | * In rare cases, fscrypt can be using an IV generation method that allows the | |
452 | * DUN to wrap around within logically contiguous blocks, and that wraparound | |
453 | * will occur. If this happens, a value less than @nr_blocks will be returned | |
454 | * so that the wraparound doesn't occur in the middle of a bio, which would | |
455 | * cause encryption/decryption to produce wrong results. | |
456 | * | |
457 | * Return: the actual number of blocks that can be submitted | |
458 | */ | |
459 | u64 fscrypt_limit_io_blocks(const struct inode *inode, u64 lblk, u64 nr_blocks) | |
460 | { | |
3e7807d5 | 461 | const struct fscrypt_inode_info *ci; |
c6c89783 EB |
462 | u32 dun; |
463 | ||
464 | if (!fscrypt_inode_uses_inline_crypto(inode)) | |
465 | return nr_blocks; | |
466 | ||
467 | if (nr_blocks <= 1) | |
468 | return nr_blocks; | |
469 | ||
470 | ci = inode->i_crypt_info; | |
471 | if (!(fscrypt_policy_flags(&ci->ci_policy) & | |
472 | FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) | |
473 | return nr_blocks; | |
474 | ||
475 | /* With IV_INO_LBLK_32, the DUN can wrap around from U32_MAX to 0. */ | |
476 | ||
477 | dun = ci->ci_hashed_ino + lblk; | |
478 | ||
479 | return min_t(u64, nr_blocks, (u64)U32_MAX + 1 - dun); | |
480 | } | |
481 | EXPORT_SYMBOL_GPL(fscrypt_limit_io_blocks); |