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1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * This contains encryption functions for per-file encryption.
4 *
5 * Copyright (C) 2015, Google, Inc.
6 * Copyright (C) 2015, Motorola Mobility
7 *
8 * Written by Michael Halcrow, 2014.
9 *
10 * Filename encryption additions
11 * Uday Savagaonkar, 2014
12 * Encryption policy handling additions
13 * Ildar Muslukhov, 2014
14 * Add fscrypt_pullback_bio_page()
15 * Jaegeuk Kim, 2015.
16 *
17 * This has not yet undergone a rigorous security audit.
18 *
19 * The usage of AES-XTS should conform to recommendations in NIST
20 * Special Publication 800-38E and IEEE P1619/D16.
21 */
22
23#include <linux/pagemap.h>
24#include <linux/mempool.h>
25#include <linux/module.h>
26#include <linux/scatterlist.h>
27#include <linux/ratelimit.h>
28#include <linux/dcache.h>
29#include <linux/namei.h>
30#include <crypto/aes.h>
31#include <crypto/skcipher.h>
32#include "fscrypt_private.h"
33
34static unsigned int num_prealloc_crypto_pages = 32;
35static unsigned int num_prealloc_crypto_ctxs = 128;
36
37module_param(num_prealloc_crypto_pages, uint, 0444);
38MODULE_PARM_DESC(num_prealloc_crypto_pages,
39 "Number of crypto pages to preallocate");
40module_param(num_prealloc_crypto_ctxs, uint, 0444);
41MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
42 "Number of crypto contexts to preallocate");
43
44static mempool_t *fscrypt_bounce_page_pool = NULL;
45
46static LIST_HEAD(fscrypt_free_ctxs);
47static DEFINE_SPINLOCK(fscrypt_ctx_lock);
48
49static struct workqueue_struct *fscrypt_read_workqueue;
50static DEFINE_MUTEX(fscrypt_init_mutex);
51
52static struct kmem_cache *fscrypt_ctx_cachep;
53struct kmem_cache *fscrypt_info_cachep;
54
55void fscrypt_enqueue_decrypt_work(struct work_struct *work)
56{
57 queue_work(fscrypt_read_workqueue, work);
58}
59EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
60
61/**
62 * fscrypt_release_ctx() - Release a decryption context
63 * @ctx: The decryption context to release.
64 *
65 * If the decryption context was allocated from the pre-allocated pool, return
66 * it to that pool. Else, free it.
67 */
68void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
69{
70 unsigned long flags;
71
72 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
73 kmem_cache_free(fscrypt_ctx_cachep, ctx);
74 } else {
75 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
76 list_add(&ctx->free_list, &fscrypt_free_ctxs);
77 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
78 }
79}
80EXPORT_SYMBOL(fscrypt_release_ctx);
81
82/**
83 * fscrypt_get_ctx() - Get a decryption context
84 * @gfp_flags: The gfp flag for memory allocation
85 *
86 * Allocate and initialize a decryption context.
87 *
88 * Return: A new decryption context on success; an ERR_PTR() otherwise.
89 */
90struct fscrypt_ctx *fscrypt_get_ctx(gfp_t gfp_flags)
91{
92 struct fscrypt_ctx *ctx;
93 unsigned long flags;
94
95 /*
96 * First try getting a ctx from the free list so that we don't have to
97 * call into the slab allocator.
98 */
99 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
100 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
101 struct fscrypt_ctx, free_list);
102 if (ctx)
103 list_del(&ctx->free_list);
104 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
105 if (!ctx) {
106 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
107 if (!ctx)
108 return ERR_PTR(-ENOMEM);
109 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
110 } else {
111 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
112 }
113 return ctx;
114}
115EXPORT_SYMBOL(fscrypt_get_ctx);
116
117struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
118{
119 return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
120}
121
122/**
123 * fscrypt_free_bounce_page() - free a ciphertext bounce page
124 *
125 * Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
126 * or by fscrypt_alloc_bounce_page() directly.
127 */
128void fscrypt_free_bounce_page(struct page *bounce_page)
129{
130 if (!bounce_page)
131 return;
132 set_page_private(bounce_page, (unsigned long)NULL);
133 ClearPagePrivate(bounce_page);
134 mempool_free(bounce_page, fscrypt_bounce_page_pool);
135}
136EXPORT_SYMBOL(fscrypt_free_bounce_page);
137
138void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
139 const struct fscrypt_info *ci)
140{
141 memset(iv, 0, ci->ci_mode->ivsize);
142 iv->lblk_num = cpu_to_le64(lblk_num);
143
144 if (fscrypt_is_direct_key_policy(&ci->ci_policy))
145 memcpy(iv->nonce, ci->ci_nonce, FS_KEY_DERIVATION_NONCE_SIZE);
146
147 if (ci->ci_essiv_tfm != NULL)
148 crypto_cipher_encrypt_one(ci->ci_essiv_tfm, iv->raw, iv->raw);
149}
150
151/* Encrypt or decrypt a single filesystem block of file contents */
152int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
153 u64 lblk_num, struct page *src_page,
154 struct page *dest_page, unsigned int len,
155 unsigned int offs, gfp_t gfp_flags)
156{
157 union fscrypt_iv iv;
158 struct skcipher_request *req = NULL;
159 DECLARE_CRYPTO_WAIT(wait);
160 struct scatterlist dst, src;
161 struct fscrypt_info *ci = inode->i_crypt_info;
162 struct crypto_skcipher *tfm = ci->ci_ctfm;
163 int res = 0;
164
165 if (WARN_ON_ONCE(len <= 0))
166 return -EINVAL;
167 if (WARN_ON_ONCE(len % FS_CRYPTO_BLOCK_SIZE != 0))
168 return -EINVAL;
169
170 fscrypt_generate_iv(&iv, lblk_num, ci);
171
172 req = skcipher_request_alloc(tfm, gfp_flags);
173 if (!req)
174 return -ENOMEM;
175
176 skcipher_request_set_callback(
177 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
178 crypto_req_done, &wait);
179
180 sg_init_table(&dst, 1);
181 sg_set_page(&dst, dest_page, len, offs);
182 sg_init_table(&src, 1);
183 sg_set_page(&src, src_page, len, offs);
184 skcipher_request_set_crypt(req, &src, &dst, len, &iv);
185 if (rw == FS_DECRYPT)
186 res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
187 else
188 res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
189 skcipher_request_free(req);
190 if (res) {
191 fscrypt_err(inode, "%scryption failed for block %llu: %d",
192 (rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
193 return res;
194 }
195 return 0;
196}
197
198/**
199 * fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a pagecache page
200 * @page: The locked pagecache page containing the block(s) to encrypt
201 * @len: Total size of the block(s) to encrypt. Must be a nonzero
202 * multiple of the filesystem's block size.
203 * @offs: Byte offset within @page of the first block to encrypt. Must be
204 * a multiple of the filesystem's block size.
205 * @gfp_flags: Memory allocation flags
206 *
207 * A new bounce page is allocated, and the specified block(s) are encrypted into
208 * it. In the bounce page, the ciphertext block(s) will be located at the same
209 * offsets at which the plaintext block(s) were located in the source page; any
210 * other parts of the bounce page will be left uninitialized. However, normally
211 * blocksize == PAGE_SIZE and the whole page is encrypted at once.
212 *
213 * This is for use by the filesystem's ->writepages() method.
214 *
215 * Return: the new encrypted bounce page on success; an ERR_PTR() on failure
216 */
217struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
218 unsigned int len,
219 unsigned int offs,
220 gfp_t gfp_flags)
221
222{
223 const struct inode *inode = page->mapping->host;
224 const unsigned int blockbits = inode->i_blkbits;
225 const unsigned int blocksize = 1 << blockbits;
226 struct page *ciphertext_page;
227 u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
228 (offs >> blockbits);
229 unsigned int i;
230 int err;
231
232 if (WARN_ON_ONCE(!PageLocked(page)))
233 return ERR_PTR(-EINVAL);
234
235 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
236 return ERR_PTR(-EINVAL);
237
238 ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
239 if (!ciphertext_page)
240 return ERR_PTR(-ENOMEM);
241
242 for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
243 err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
244 page, ciphertext_page,
245 blocksize, i, gfp_flags);
246 if (err) {
247 fscrypt_free_bounce_page(ciphertext_page);
248 return ERR_PTR(err);
249 }
250 }
251 SetPagePrivate(ciphertext_page);
252 set_page_private(ciphertext_page, (unsigned long)page);
253 return ciphertext_page;
254}
255EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
256
257/**
258 * fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
259 * @inode: The inode to which this block belongs
260 * @page: The page containing the block to encrypt
261 * @len: Size of block to encrypt. Doesn't need to be a multiple of the
262 * fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
263 * @offs: Byte offset within @page at which the block to encrypt begins
264 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
265 * number of the block within the file
266 * @gfp_flags: Memory allocation flags
267 *
268 * Encrypt a possibly-compressed filesystem block that is located in an
269 * arbitrary page, not necessarily in the original pagecache page. The @inode
270 * and @lblk_num must be specified, as they can't be determined from @page.
271 *
272 * Return: 0 on success; -errno on failure
273 */
274int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
275 unsigned int len, unsigned int offs,
276 u64 lblk_num, gfp_t gfp_flags)
277{
278 return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
279 len, offs, gfp_flags);
280}
281EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
282
283/**
284 * fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a pagecache page
285 * @page: The locked pagecache page containing the block(s) to decrypt
286 * @len: Total size of the block(s) to decrypt. Must be a nonzero
287 * multiple of the filesystem's block size.
288 * @offs: Byte offset within @page of the first block to decrypt. Must be
289 * a multiple of the filesystem's block size.
290 *
291 * The specified block(s) are decrypted in-place within the pagecache page,
292 * which must still be locked and not uptodate. Normally, blocksize ==
293 * PAGE_SIZE and the whole page is decrypted at once.
294 *
295 * This is for use by the filesystem's ->readpages() method.
296 *
297 * Return: 0 on success; -errno on failure
298 */
299int fscrypt_decrypt_pagecache_blocks(struct page *page, unsigned int len,
300 unsigned int offs)
301{
302 const struct inode *inode = page->mapping->host;
303 const unsigned int blockbits = inode->i_blkbits;
304 const unsigned int blocksize = 1 << blockbits;
305 u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
306 (offs >> blockbits);
307 unsigned int i;
308 int err;
309
310 if (WARN_ON_ONCE(!PageLocked(page)))
311 return -EINVAL;
312
313 if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
314 return -EINVAL;
315
316 for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
317 err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
318 page, blocksize, i, GFP_NOFS);
319 if (err)
320 return err;
321 }
322 return 0;
323}
324EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
325
326/**
327 * fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
328 * @inode: The inode to which this block belongs
329 * @page: The page containing the block to decrypt
330 * @len: Size of block to decrypt. Doesn't need to be a multiple of the
331 * fs block size, but must be a multiple of FS_CRYPTO_BLOCK_SIZE.
332 * @offs: Byte offset within @page at which the block to decrypt begins
333 * @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
334 * number of the block within the file
335 *
336 * Decrypt a possibly-compressed filesystem block that is located in an
337 * arbitrary page, not necessarily in the original pagecache page. The @inode
338 * and @lblk_num must be specified, as they can't be determined from @page.
339 *
340 * Return: 0 on success; -errno on failure
341 */
342int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
343 unsigned int len, unsigned int offs,
344 u64 lblk_num)
345{
346 return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
347 len, offs, GFP_NOFS);
348}
349EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
350
351/*
352 * Validate dentries in encrypted directories to make sure we aren't potentially
353 * caching stale dentries after a key has been added.
354 */
355static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
356{
357 struct dentry *dir;
358 int err;
359 int valid;
360
361 /*
362 * Plaintext names are always valid, since fscrypt doesn't support
363 * reverting to ciphertext names without evicting the directory's inode
364 * -- which implies eviction of the dentries in the directory.
365 */
366 if (!(dentry->d_flags & DCACHE_ENCRYPTED_NAME))
367 return 1;
368
369 /*
370 * Ciphertext name; valid if the directory's key is still unavailable.
371 *
372 * Although fscrypt forbids rename() on ciphertext names, we still must
373 * use dget_parent() here rather than use ->d_parent directly. That's
374 * because a corrupted fs image may contain directory hard links, which
375 * the VFS handles by moving the directory's dentry tree in the dcache
376 * each time ->lookup() finds the directory and it already has a dentry
377 * elsewhere. Thus ->d_parent can be changing, and we must safely grab
378 * a reference to some ->d_parent to prevent it from being freed.
379 */
380
381 if (flags & LOOKUP_RCU)
382 return -ECHILD;
383
384 dir = dget_parent(dentry);
385 err = fscrypt_get_encryption_info(d_inode(dir));
386 valid = !fscrypt_has_encryption_key(d_inode(dir));
387 dput(dir);
388
389 if (err < 0)
390 return err;
391
392 return valid;
393}
394
395const struct dentry_operations fscrypt_d_ops = {
396 .d_revalidate = fscrypt_d_revalidate,
397};
398
399static void fscrypt_destroy(void)
400{
401 struct fscrypt_ctx *pos, *n;
402
403 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
404 kmem_cache_free(fscrypt_ctx_cachep, pos);
405 INIT_LIST_HEAD(&fscrypt_free_ctxs);
406 mempool_destroy(fscrypt_bounce_page_pool);
407 fscrypt_bounce_page_pool = NULL;
408}
409
410/**
411 * fscrypt_initialize() - allocate major buffers for fs encryption.
412 * @cop_flags: fscrypt operations flags
413 *
414 * We only call this when we start accessing encrypted files, since it
415 * results in memory getting allocated that wouldn't otherwise be used.
416 *
417 * Return: Zero on success, non-zero otherwise.
418 */
419int fscrypt_initialize(unsigned int cop_flags)
420{
421 int i, res = -ENOMEM;
422
423 /* No need to allocate a bounce page pool if this FS won't use it. */
424 if (cop_flags & FS_CFLG_OWN_PAGES)
425 return 0;
426
427 mutex_lock(&fscrypt_init_mutex);
428 if (fscrypt_bounce_page_pool)
429 goto already_initialized;
430
431 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
432 struct fscrypt_ctx *ctx;
433
434 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
435 if (!ctx)
436 goto fail;
437 list_add(&ctx->free_list, &fscrypt_free_ctxs);
438 }
439
440 fscrypt_bounce_page_pool =
441 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
442 if (!fscrypt_bounce_page_pool)
443 goto fail;
444
445already_initialized:
446 mutex_unlock(&fscrypt_init_mutex);
447 return 0;
448fail:
449 fscrypt_destroy();
450 mutex_unlock(&fscrypt_init_mutex);
451 return res;
452}
453
454void fscrypt_msg(const struct inode *inode, const char *level,
455 const char *fmt, ...)
456{
457 static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
458 DEFAULT_RATELIMIT_BURST);
459 struct va_format vaf;
460 va_list args;
461
462 if (!__ratelimit(&rs))
463 return;
464
465 va_start(args, fmt);
466 vaf.fmt = fmt;
467 vaf.va = &args;
468 if (inode)
469 printk("%sfscrypt (%s, inode %lu): %pV\n",
470 level, inode->i_sb->s_id, inode->i_ino, &vaf);
471 else
472 printk("%sfscrypt: %pV\n", level, &vaf);
473 va_end(args);
474}
475
476/**
477 * fscrypt_init() - Set up for fs encryption.
478 */
479static int __init fscrypt_init(void)
480{
481 int err = -ENOMEM;
482
483 /*
484 * Use an unbound workqueue to allow bios to be decrypted in parallel
485 * even when they happen to complete on the same CPU. This sacrifices
486 * locality, but it's worthwhile since decryption is CPU-intensive.
487 *
488 * Also use a high-priority workqueue to prioritize decryption work,
489 * which blocks reads from completing, over regular application tasks.
490 */
491 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
492 WQ_UNBOUND | WQ_HIGHPRI,
493 num_online_cpus());
494 if (!fscrypt_read_workqueue)
495 goto fail;
496
497 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
498 if (!fscrypt_ctx_cachep)
499 goto fail_free_queue;
500
501 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
502 if (!fscrypt_info_cachep)
503 goto fail_free_ctx;
504
505 err = fscrypt_init_keyring();
506 if (err)
507 goto fail_free_info;
508
509 return 0;
510
511fail_free_info:
512 kmem_cache_destroy(fscrypt_info_cachep);
513fail_free_ctx:
514 kmem_cache_destroy(fscrypt_ctx_cachep);
515fail_free_queue:
516 destroy_workqueue(fscrypt_read_workqueue);
517fail:
518 return err;
519}
520late_initcall(fscrypt_init)
1/*
2 * This contains encryption functions for per-file encryption.
3 *
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
6 *
7 * Written by Michael Halcrow, 2014.
8 *
9 * Filename encryption additions
10 * Uday Savagaonkar, 2014
11 * Encryption policy handling additions
12 * Ildar Muslukhov, 2014
13 * Add fscrypt_pullback_bio_page()
14 * Jaegeuk Kim, 2015.
15 *
16 * This has not yet undergone a rigorous security audit.
17 *
18 * The usage of AES-XTS should conform to recommendations in NIST
19 * Special Publication 800-38E and IEEE P1619/D16.
20 */
21
22#include <linux/pagemap.h>
23#include <linux/mempool.h>
24#include <linux/module.h>
25#include <linux/scatterlist.h>
26#include <linux/ratelimit.h>
27#include <linux/bio.h>
28#include <linux/dcache.h>
29#include <linux/namei.h>
30#include "fscrypt_private.h"
31
32static unsigned int num_prealloc_crypto_pages = 32;
33static unsigned int num_prealloc_crypto_ctxs = 128;
34
35module_param(num_prealloc_crypto_pages, uint, 0444);
36MODULE_PARM_DESC(num_prealloc_crypto_pages,
37 "Number of crypto pages to preallocate");
38module_param(num_prealloc_crypto_ctxs, uint, 0444);
39MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
40 "Number of crypto contexts to preallocate");
41
42static mempool_t *fscrypt_bounce_page_pool = NULL;
43
44static LIST_HEAD(fscrypt_free_ctxs);
45static DEFINE_SPINLOCK(fscrypt_ctx_lock);
46
47static struct workqueue_struct *fscrypt_read_workqueue;
48static DEFINE_MUTEX(fscrypt_init_mutex);
49
50static struct kmem_cache *fscrypt_ctx_cachep;
51struct kmem_cache *fscrypt_info_cachep;
52
53/**
54 * fscrypt_release_ctx() - Releases an encryption context
55 * @ctx: The encryption context to release.
56 *
57 * If the encryption context was allocated from the pre-allocated pool, returns
58 * it to that pool. Else, frees it.
59 *
60 * If there's a bounce page in the context, this frees that.
61 */
62void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
63{
64 unsigned long flags;
65
66 if (ctx->flags & FS_CTX_HAS_BOUNCE_BUFFER_FL && ctx->w.bounce_page) {
67 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
68 ctx->w.bounce_page = NULL;
69 }
70 ctx->w.control_page = NULL;
71 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
72 kmem_cache_free(fscrypt_ctx_cachep, ctx);
73 } else {
74 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
75 list_add(&ctx->free_list, &fscrypt_free_ctxs);
76 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
77 }
78}
79EXPORT_SYMBOL(fscrypt_release_ctx);
80
81/**
82 * fscrypt_get_ctx() - Gets an encryption context
83 * @inode: The inode for which we are doing the crypto
84 * @gfp_flags: The gfp flag for memory allocation
85 *
86 * Allocates and initializes an encryption context.
87 *
88 * Return: An allocated and initialized encryption context on success; error
89 * value or NULL otherwise.
90 */
91struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
92{
93 struct fscrypt_ctx *ctx = NULL;
94 struct fscrypt_info *ci = inode->i_crypt_info;
95 unsigned long flags;
96
97 if (ci == NULL)
98 return ERR_PTR(-ENOKEY);
99
100 /*
101 * We first try getting the ctx from a free list because in
102 * the common case the ctx will have an allocated and
103 * initialized crypto tfm, so it's probably a worthwhile
104 * optimization. For the bounce page, we first try getting it
105 * from the kernel allocator because that's just about as fast
106 * as getting it from a list and because a cache of free pages
107 * should generally be a "last resort" option for a filesystem
108 * to be able to do its job.
109 */
110 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
111 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
112 struct fscrypt_ctx, free_list);
113 if (ctx)
114 list_del(&ctx->free_list);
115 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
116 if (!ctx) {
117 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
118 if (!ctx)
119 return ERR_PTR(-ENOMEM);
120 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
121 } else {
122 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
123 }
124 ctx->flags &= ~FS_CTX_HAS_BOUNCE_BUFFER_FL;
125 return ctx;
126}
127EXPORT_SYMBOL(fscrypt_get_ctx);
128
129/**
130 * page_crypt_complete() - completion callback for page crypto
131 * @req: The asynchronous cipher request context
132 * @res: The result of the cipher operation
133 */
134static void page_crypt_complete(struct crypto_async_request *req, int res)
135{
136 struct fscrypt_completion_result *ecr = req->data;
137
138 if (res == -EINPROGRESS)
139 return;
140 ecr->res = res;
141 complete(&ecr->completion);
142}
143
144typedef enum {
145 FS_DECRYPT = 0,
146 FS_ENCRYPT,
147} fscrypt_direction_t;
148
149static int do_page_crypto(const struct inode *inode,
150 fscrypt_direction_t rw, u64 lblk_num,
151 struct page *src_page, struct page *dest_page,
152 unsigned int len, unsigned int offs,
153 gfp_t gfp_flags)
154{
155 struct {
156 __le64 index;
157 u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
158 } xts_tweak;
159 struct skcipher_request *req = NULL;
160 DECLARE_FS_COMPLETION_RESULT(ecr);
161 struct scatterlist dst, src;
162 struct fscrypt_info *ci = inode->i_crypt_info;
163 struct crypto_skcipher *tfm = ci->ci_ctfm;
164 int res = 0;
165
166 BUG_ON(len == 0);
167
168 req = skcipher_request_alloc(tfm, gfp_flags);
169 if (!req) {
170 printk_ratelimited(KERN_ERR
171 "%s: crypto_request_alloc() failed\n",
172 __func__);
173 return -ENOMEM;
174 }
175
176 skcipher_request_set_callback(
177 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
178 page_crypt_complete, &ecr);
179
180 BUILD_BUG_ON(sizeof(xts_tweak) != FS_XTS_TWEAK_SIZE);
181 xts_tweak.index = cpu_to_le64(lblk_num);
182 memset(xts_tweak.padding, 0, sizeof(xts_tweak.padding));
183
184 sg_init_table(&dst, 1);
185 sg_set_page(&dst, dest_page, len, offs);
186 sg_init_table(&src, 1);
187 sg_set_page(&src, src_page, len, offs);
188 skcipher_request_set_crypt(req, &src, &dst, len, &xts_tweak);
189 if (rw == FS_DECRYPT)
190 res = crypto_skcipher_decrypt(req);
191 else
192 res = crypto_skcipher_encrypt(req);
193 if (res == -EINPROGRESS || res == -EBUSY) {
194 BUG_ON(req->base.data != &ecr);
195 wait_for_completion(&ecr.completion);
196 res = ecr.res;
197 }
198 skcipher_request_free(req);
199 if (res) {
200 printk_ratelimited(KERN_ERR
201 "%s: crypto_skcipher_encrypt() returned %d\n",
202 __func__, res);
203 return res;
204 }
205 return 0;
206}
207
208static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
209{
210 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
211 if (ctx->w.bounce_page == NULL)
212 return ERR_PTR(-ENOMEM);
213 ctx->flags |= FS_CTX_HAS_BOUNCE_BUFFER_FL;
214 return ctx->w.bounce_page;
215}
216
217/**
218 * fscypt_encrypt_page() - Encrypts a page
219 * @inode: The inode for which the encryption should take place
220 * @page: The page to encrypt. Must be locked for bounce-page
221 * encryption.
222 * @len: Length of data to encrypt in @page and encrypted
223 * data in returned page.
224 * @offs: Offset of data within @page and returned
225 * page holding encrypted data.
226 * @lblk_num: Logical block number. This must be unique for multiple
227 * calls with same inode, except when overwriting
228 * previously written data.
229 * @gfp_flags: The gfp flag for memory allocation
230 *
231 * Encrypts @page using the ctx encryption context. Performs encryption
232 * either in-place or into a newly allocated bounce page.
233 * Called on the page write path.
234 *
235 * Bounce page allocation is the default.
236 * In this case, the contents of @page are encrypted and stored in an
237 * allocated bounce page. @page has to be locked and the caller must call
238 * fscrypt_restore_control_page() on the returned ciphertext page to
239 * release the bounce buffer and the encryption context.
240 *
241 * In-place encryption is used by setting the FS_CFLG_OWN_PAGES flag in
242 * fscrypt_operations. Here, the input-page is returned with its content
243 * encrypted.
244 *
245 * Return: A page with the encrypted content on success. Else, an
246 * error value or NULL.
247 */
248struct page *fscrypt_encrypt_page(const struct inode *inode,
249 struct page *page,
250 unsigned int len,
251 unsigned int offs,
252 u64 lblk_num, gfp_t gfp_flags)
253
254{
255 struct fscrypt_ctx *ctx;
256 struct page *ciphertext_page = page;
257 int err;
258
259 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
260
261 if (inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES) {
262 /* with inplace-encryption we just encrypt the page */
263 err = do_page_crypto(inode, FS_ENCRYPT, lblk_num,
264 page, ciphertext_page,
265 len, offs, gfp_flags);
266 if (err)
267 return ERR_PTR(err);
268
269 return ciphertext_page;
270 }
271
272 BUG_ON(!PageLocked(page));
273
274 ctx = fscrypt_get_ctx(inode, gfp_flags);
275 if (IS_ERR(ctx))
276 return (struct page *)ctx;
277
278 /* The encryption operation will require a bounce page. */
279 ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
280 if (IS_ERR(ciphertext_page))
281 goto errout;
282
283 ctx->w.control_page = page;
284 err = do_page_crypto(inode, FS_ENCRYPT, lblk_num,
285 page, ciphertext_page,
286 len, offs, gfp_flags);
287 if (err) {
288 ciphertext_page = ERR_PTR(err);
289 goto errout;
290 }
291 SetPagePrivate(ciphertext_page);
292 set_page_private(ciphertext_page, (unsigned long)ctx);
293 lock_page(ciphertext_page);
294 return ciphertext_page;
295
296errout:
297 fscrypt_release_ctx(ctx);
298 return ciphertext_page;
299}
300EXPORT_SYMBOL(fscrypt_encrypt_page);
301
302/**
303 * fscrypt_decrypt_page() - Decrypts a page in-place
304 * @inode: The corresponding inode for the page to decrypt.
305 * @page: The page to decrypt. Must be locked in case
306 * it is a writeback page (FS_CFLG_OWN_PAGES unset).
307 * @len: Number of bytes in @page to be decrypted.
308 * @offs: Start of data in @page.
309 * @lblk_num: Logical block number.
310 *
311 * Decrypts page in-place using the ctx encryption context.
312 *
313 * Called from the read completion callback.
314 *
315 * Return: Zero on success, non-zero otherwise.
316 */
317int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
318 unsigned int len, unsigned int offs, u64 lblk_num)
319{
320 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
321 BUG_ON(!PageLocked(page));
322
323 return do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page, len,
324 offs, GFP_NOFS);
325}
326EXPORT_SYMBOL(fscrypt_decrypt_page);
327
328int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
329 sector_t pblk, unsigned int len)
330{
331 struct fscrypt_ctx *ctx;
332 struct page *ciphertext_page = NULL;
333 struct bio *bio;
334 int ret, err = 0;
335
336 BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
337
338 ctx = fscrypt_get_ctx(inode, GFP_NOFS);
339 if (IS_ERR(ctx))
340 return PTR_ERR(ctx);
341
342 ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
343 if (IS_ERR(ciphertext_page)) {
344 err = PTR_ERR(ciphertext_page);
345 goto errout;
346 }
347
348 while (len--) {
349 err = do_page_crypto(inode, FS_ENCRYPT, lblk,
350 ZERO_PAGE(0), ciphertext_page,
351 PAGE_SIZE, 0, GFP_NOFS);
352 if (err)
353 goto errout;
354
355 bio = bio_alloc(GFP_NOWAIT, 1);
356 if (!bio) {
357 err = -ENOMEM;
358 goto errout;
359 }
360 bio->bi_bdev = inode->i_sb->s_bdev;
361 bio->bi_iter.bi_sector =
362 pblk << (inode->i_sb->s_blocksize_bits - 9);
363 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
364 ret = bio_add_page(bio, ciphertext_page,
365 inode->i_sb->s_blocksize, 0);
366 if (ret != inode->i_sb->s_blocksize) {
367 /* should never happen! */
368 WARN_ON(1);
369 bio_put(bio);
370 err = -EIO;
371 goto errout;
372 }
373 err = submit_bio_wait(bio);
374 if ((err == 0) && bio->bi_error)
375 err = -EIO;
376 bio_put(bio);
377 if (err)
378 goto errout;
379 lblk++;
380 pblk++;
381 }
382 err = 0;
383errout:
384 fscrypt_release_ctx(ctx);
385 return err;
386}
387EXPORT_SYMBOL(fscrypt_zeroout_range);
388
389/*
390 * Validate dentries for encrypted directories to make sure we aren't
391 * potentially caching stale data after a key has been added or
392 * removed.
393 */
394static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
395{
396 struct dentry *dir;
397 int dir_has_key, cached_with_key;
398
399 if (flags & LOOKUP_RCU)
400 return -ECHILD;
401
402 dir = dget_parent(dentry);
403 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
404 dput(dir);
405 return 0;
406 }
407
408 /* this should eventually be an flag in d_flags */
409 spin_lock(&dentry->d_lock);
410 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
411 spin_unlock(&dentry->d_lock);
412 dir_has_key = (d_inode(dir)->i_crypt_info != NULL);
413 dput(dir);
414
415 /*
416 * If the dentry was cached without the key, and it is a
417 * negative dentry, it might be a valid name. We can't check
418 * if the key has since been made available due to locking
419 * reasons, so we fail the validation so ext4_lookup() can do
420 * this check.
421 *
422 * We also fail the validation if the dentry was created with
423 * the key present, but we no longer have the key, or vice versa.
424 */
425 if ((!cached_with_key && d_is_negative(dentry)) ||
426 (!cached_with_key && dir_has_key) ||
427 (cached_with_key && !dir_has_key))
428 return 0;
429 return 1;
430}
431
432const struct dentry_operations fscrypt_d_ops = {
433 .d_revalidate = fscrypt_d_revalidate,
434};
435EXPORT_SYMBOL(fscrypt_d_ops);
436
437/*
438 * Call fscrypt_decrypt_page on every single page, reusing the encryption
439 * context.
440 */
441static void completion_pages(struct work_struct *work)
442{
443 struct fscrypt_ctx *ctx =
444 container_of(work, struct fscrypt_ctx, r.work);
445 struct bio *bio = ctx->r.bio;
446 struct bio_vec *bv;
447 int i;
448
449 bio_for_each_segment_all(bv, bio, i) {
450 struct page *page = bv->bv_page;
451 int ret = fscrypt_decrypt_page(page->mapping->host, page,
452 PAGE_SIZE, 0, page->index);
453
454 if (ret) {
455 WARN_ON_ONCE(1);
456 SetPageError(page);
457 } else {
458 SetPageUptodate(page);
459 }
460 unlock_page(page);
461 }
462 fscrypt_release_ctx(ctx);
463 bio_put(bio);
464}
465
466void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
467{
468 INIT_WORK(&ctx->r.work, completion_pages);
469 ctx->r.bio = bio;
470 queue_work(fscrypt_read_workqueue, &ctx->r.work);
471}
472EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
473
474void fscrypt_pullback_bio_page(struct page **page, bool restore)
475{
476 struct fscrypt_ctx *ctx;
477 struct page *bounce_page;
478
479 /* The bounce data pages are unmapped. */
480 if ((*page)->mapping)
481 return;
482
483 /* The bounce data page is unmapped. */
484 bounce_page = *page;
485 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
486
487 /* restore control page */
488 *page = ctx->w.control_page;
489
490 if (restore)
491 fscrypt_restore_control_page(bounce_page);
492}
493EXPORT_SYMBOL(fscrypt_pullback_bio_page);
494
495void fscrypt_restore_control_page(struct page *page)
496{
497 struct fscrypt_ctx *ctx;
498
499 ctx = (struct fscrypt_ctx *)page_private(page);
500 set_page_private(page, (unsigned long)NULL);
501 ClearPagePrivate(page);
502 unlock_page(page);
503 fscrypt_release_ctx(ctx);
504}
505EXPORT_SYMBOL(fscrypt_restore_control_page);
506
507static void fscrypt_destroy(void)
508{
509 struct fscrypt_ctx *pos, *n;
510
511 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
512 kmem_cache_free(fscrypt_ctx_cachep, pos);
513 INIT_LIST_HEAD(&fscrypt_free_ctxs);
514 mempool_destroy(fscrypt_bounce_page_pool);
515 fscrypt_bounce_page_pool = NULL;
516}
517
518/**
519 * fscrypt_initialize() - allocate major buffers for fs encryption.
520 * @cop_flags: fscrypt operations flags
521 *
522 * We only call this when we start accessing encrypted files, since it
523 * results in memory getting allocated that wouldn't otherwise be used.
524 *
525 * Return: Zero on success, non-zero otherwise.
526 */
527int fscrypt_initialize(unsigned int cop_flags)
528{
529 int i, res = -ENOMEM;
530
531 /*
532 * No need to allocate a bounce page pool if there already is one or
533 * this FS won't use it.
534 */
535 if (cop_flags & FS_CFLG_OWN_PAGES || fscrypt_bounce_page_pool)
536 return 0;
537
538 mutex_lock(&fscrypt_init_mutex);
539 if (fscrypt_bounce_page_pool)
540 goto already_initialized;
541
542 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
543 struct fscrypt_ctx *ctx;
544
545 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
546 if (!ctx)
547 goto fail;
548 list_add(&ctx->free_list, &fscrypt_free_ctxs);
549 }
550
551 fscrypt_bounce_page_pool =
552 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
553 if (!fscrypt_bounce_page_pool)
554 goto fail;
555
556already_initialized:
557 mutex_unlock(&fscrypt_init_mutex);
558 return 0;
559fail:
560 fscrypt_destroy();
561 mutex_unlock(&fscrypt_init_mutex);
562 return res;
563}
564
565/**
566 * fscrypt_init() - Set up for fs encryption.
567 */
568static int __init fscrypt_init(void)
569{
570 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
571 WQ_HIGHPRI, 0);
572 if (!fscrypt_read_workqueue)
573 goto fail;
574
575 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
576 if (!fscrypt_ctx_cachep)
577 goto fail_free_queue;
578
579 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
580 if (!fscrypt_info_cachep)
581 goto fail_free_ctx;
582
583 return 0;
584
585fail_free_ctx:
586 kmem_cache_destroy(fscrypt_ctx_cachep);
587fail_free_queue:
588 destroy_workqueue(fscrypt_read_workqueue);
589fail:
590 return -ENOMEM;
591}
592module_init(fscrypt_init)
593
594/**
595 * fscrypt_exit() - Shutdown the fs encryption system
596 */
597static void __exit fscrypt_exit(void)
598{
599 fscrypt_destroy();
600
601 if (fscrypt_read_workqueue)
602 destroy_workqueue(fscrypt_read_workqueue);
603 kmem_cache_destroy(fscrypt_ctx_cachep);
604 kmem_cache_destroy(fscrypt_info_cachep);
605}
606module_exit(fscrypt_exit);
607
608MODULE_LICENSE("GPL");