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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 <linux/fscrypto.h>
31#include <linux/ecryptfs.h>
32
33static unsigned int num_prealloc_crypto_pages = 32;
34static unsigned int num_prealloc_crypto_ctxs = 128;
35
36module_param(num_prealloc_crypto_pages, uint, 0444);
37MODULE_PARM_DESC(num_prealloc_crypto_pages,
38 "Number of crypto pages to preallocate");
39module_param(num_prealloc_crypto_ctxs, uint, 0444);
40MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
41 "Number of crypto contexts to preallocate");
42
43static mempool_t *fscrypt_bounce_page_pool = NULL;
44
45static LIST_HEAD(fscrypt_free_ctxs);
46static DEFINE_SPINLOCK(fscrypt_ctx_lock);
47
48static struct workqueue_struct *fscrypt_read_workqueue;
49static DEFINE_MUTEX(fscrypt_init_mutex);
50
51static struct kmem_cache *fscrypt_ctx_cachep;
52struct kmem_cache *fscrypt_info_cachep;
53
54/**
55 * fscrypt_release_ctx() - Releases an encryption context
56 * @ctx: The encryption context to release.
57 *
58 * If the encryption context was allocated from the pre-allocated pool, returns
59 * it to that pool. Else, frees it.
60 *
61 * If there's a bounce page in the context, this frees that.
62 */
63void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
64{
65 unsigned long flags;
66
67 if (ctx->flags & FS_WRITE_PATH_FL && ctx->w.bounce_page) {
68 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
69 ctx->w.bounce_page = NULL;
70 }
71 ctx->w.control_page = NULL;
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() - Gets an encryption context
84 * @inode: The inode for which we are doing the crypto
85 * @gfp_flags: The gfp flag for memory allocation
86 *
87 * Allocates and initializes an encryption context.
88 *
89 * Return: An allocated and initialized encryption context on success; error
90 * value or NULL otherwise.
91 */
92struct fscrypt_ctx *fscrypt_get_ctx(struct inode *inode, gfp_t gfp_flags)
93{
94 struct fscrypt_ctx *ctx = NULL;
95 struct fscrypt_info *ci = inode->i_crypt_info;
96 unsigned long flags;
97
98 if (ci == NULL)
99 return ERR_PTR(-ENOKEY);
100
101 /*
102 * We first try getting the ctx from a free list because in
103 * the common case the ctx will have an allocated and
104 * initialized crypto tfm, so it's probably a worthwhile
105 * optimization. For the bounce page, we first try getting it
106 * from the kernel allocator because that's just about as fast
107 * as getting it from a list and because a cache of free pages
108 * should generally be a "last resort" option for a filesystem
109 * to be able to do its job.
110 */
111 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
112 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
113 struct fscrypt_ctx, free_list);
114 if (ctx)
115 list_del(&ctx->free_list);
116 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
117 if (!ctx) {
118 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
119 if (!ctx)
120 return ERR_PTR(-ENOMEM);
121 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
122 } else {
123 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
124 }
125 ctx->flags &= ~FS_WRITE_PATH_FL;
126 return ctx;
127}
128EXPORT_SYMBOL(fscrypt_get_ctx);
129
130/**
131 * fscrypt_complete() - The completion callback for page encryption
132 * @req: The asynchronous encryption request context
133 * @res: The result of the encryption operation
134 */
135static void fscrypt_complete(struct crypto_async_request *req, int res)
136{
137 struct fscrypt_completion_result *ecr = req->data;
138
139 if (res == -EINPROGRESS)
140 return;
141 ecr->res = res;
142 complete(&ecr->completion);
143}
144
145typedef enum {
146 FS_DECRYPT = 0,
147 FS_ENCRYPT,
148} fscrypt_direction_t;
149
150static int do_page_crypto(struct inode *inode,
151 fscrypt_direction_t rw, pgoff_t index,
152 struct page *src_page, struct page *dest_page,
153 gfp_t gfp_flags)
154{
155 u8 xts_tweak[FS_XTS_TWEAK_SIZE];
156 struct skcipher_request *req = NULL;
157 DECLARE_FS_COMPLETION_RESULT(ecr);
158 struct scatterlist dst, src;
159 struct fscrypt_info *ci = inode->i_crypt_info;
160 struct crypto_skcipher *tfm = ci->ci_ctfm;
161 int res = 0;
162
163 req = skcipher_request_alloc(tfm, gfp_flags);
164 if (!req) {
165 printk_ratelimited(KERN_ERR
166 "%s: crypto_request_alloc() failed\n",
167 __func__);
168 return -ENOMEM;
169 }
170
171 skcipher_request_set_callback(
172 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
173 fscrypt_complete, &ecr);
174
175 BUILD_BUG_ON(FS_XTS_TWEAK_SIZE < sizeof(index));
176 memcpy(xts_tweak, &index, sizeof(index));
177 memset(&xts_tweak[sizeof(index)], 0,
178 FS_XTS_TWEAK_SIZE - sizeof(index));
179
180 sg_init_table(&dst, 1);
181 sg_set_page(&dst, dest_page, PAGE_SIZE, 0);
182 sg_init_table(&src, 1);
183 sg_set_page(&src, src_page, PAGE_SIZE, 0);
184 skcipher_request_set_crypt(req, &src, &dst, PAGE_SIZE,
185 xts_tweak);
186 if (rw == FS_DECRYPT)
187 res = crypto_skcipher_decrypt(req);
188 else
189 res = crypto_skcipher_encrypt(req);
190 if (res == -EINPROGRESS || res == -EBUSY) {
191 BUG_ON(req->base.data != &ecr);
192 wait_for_completion(&ecr.completion);
193 res = ecr.res;
194 }
195 skcipher_request_free(req);
196 if (res) {
197 printk_ratelimited(KERN_ERR
198 "%s: crypto_skcipher_encrypt() returned %d\n",
199 __func__, res);
200 return res;
201 }
202 return 0;
203}
204
205static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
206{
207 ctx->w.bounce_page = mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
208 if (ctx->w.bounce_page == NULL)
209 return ERR_PTR(-ENOMEM);
210 ctx->flags |= FS_WRITE_PATH_FL;
211 return ctx->w.bounce_page;
212}
213
214/**
215 * fscypt_encrypt_page() - Encrypts a page
216 * @inode: The inode for which the encryption should take place
217 * @plaintext_page: The page to encrypt. Must be locked.
218 * @gfp_flags: The gfp flag for memory allocation
219 *
220 * Allocates a ciphertext page and encrypts plaintext_page into it using the ctx
221 * encryption context.
222 *
223 * Called on the page write path. The caller must call
224 * fscrypt_restore_control_page() on the returned ciphertext page to
225 * release the bounce buffer and the encryption context.
226 *
227 * Return: An allocated page with the encrypted content on success. Else, an
228 * error value or NULL.
229 */
230struct page *fscrypt_encrypt_page(struct inode *inode,
231 struct page *plaintext_page, gfp_t gfp_flags)
232{
233 struct fscrypt_ctx *ctx;
234 struct page *ciphertext_page = NULL;
235 int err;
236
237 BUG_ON(!PageLocked(plaintext_page));
238
239 ctx = fscrypt_get_ctx(inode, gfp_flags);
240 if (IS_ERR(ctx))
241 return (struct page *)ctx;
242
243 /* The encryption operation will require a bounce page. */
244 ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
245 if (IS_ERR(ciphertext_page))
246 goto errout;
247
248 ctx->w.control_page = plaintext_page;
249 err = do_page_crypto(inode, FS_ENCRYPT, plaintext_page->index,
250 plaintext_page, ciphertext_page,
251 gfp_flags);
252 if (err) {
253 ciphertext_page = ERR_PTR(err);
254 goto errout;
255 }
256 SetPagePrivate(ciphertext_page);
257 set_page_private(ciphertext_page, (unsigned long)ctx);
258 lock_page(ciphertext_page);
259 return ciphertext_page;
260
261errout:
262 fscrypt_release_ctx(ctx);
263 return ciphertext_page;
264}
265EXPORT_SYMBOL(fscrypt_encrypt_page);
266
267/**
268 * f2crypt_decrypt_page() - Decrypts a page in-place
269 * @page: The page to decrypt. Must be locked.
270 *
271 * Decrypts page in-place using the ctx encryption context.
272 *
273 * Called from the read completion callback.
274 *
275 * Return: Zero on success, non-zero otherwise.
276 */
277int fscrypt_decrypt_page(struct page *page)
278{
279 BUG_ON(!PageLocked(page));
280
281 return do_page_crypto(page->mapping->host,
282 FS_DECRYPT, page->index, page, page, GFP_NOFS);
283}
284EXPORT_SYMBOL(fscrypt_decrypt_page);
285
286int fscrypt_zeroout_range(struct inode *inode, pgoff_t lblk,
287 sector_t pblk, unsigned int len)
288{
289 struct fscrypt_ctx *ctx;
290 struct page *ciphertext_page = NULL;
291 struct bio *bio;
292 int ret, err = 0;
293
294 BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
295
296 ctx = fscrypt_get_ctx(inode, GFP_NOFS);
297 if (IS_ERR(ctx))
298 return PTR_ERR(ctx);
299
300 ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
301 if (IS_ERR(ciphertext_page)) {
302 err = PTR_ERR(ciphertext_page);
303 goto errout;
304 }
305
306 while (len--) {
307 err = do_page_crypto(inode, FS_ENCRYPT, lblk,
308 ZERO_PAGE(0), ciphertext_page,
309 GFP_NOFS);
310 if (err)
311 goto errout;
312
313 bio = bio_alloc(GFP_NOWAIT, 1);
314 if (!bio) {
315 err = -ENOMEM;
316 goto errout;
317 }
318 bio->bi_bdev = inode->i_sb->s_bdev;
319 bio->bi_iter.bi_sector =
320 pblk << (inode->i_sb->s_blocksize_bits - 9);
321 ret = bio_add_page(bio, ciphertext_page,
322 inode->i_sb->s_blocksize, 0);
323 if (ret != inode->i_sb->s_blocksize) {
324 /* should never happen! */
325 WARN_ON(1);
326 bio_put(bio);
327 err = -EIO;
328 goto errout;
329 }
330 err = submit_bio_wait(WRITE, bio);
331 if ((err == 0) && bio->bi_error)
332 err = -EIO;
333 bio_put(bio);
334 if (err)
335 goto errout;
336 lblk++;
337 pblk++;
338 }
339 err = 0;
340errout:
341 fscrypt_release_ctx(ctx);
342 return err;
343}
344EXPORT_SYMBOL(fscrypt_zeroout_range);
345
346/*
347 * Validate dentries for encrypted directories to make sure we aren't
348 * potentially caching stale data after a key has been added or
349 * removed.
350 */
351static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
352{
353 struct dentry *dir;
354 struct fscrypt_info *ci;
355 int dir_has_key, cached_with_key;
356
357 if (flags & LOOKUP_RCU)
358 return -ECHILD;
359
360 dir = dget_parent(dentry);
361 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
362 dput(dir);
363 return 0;
364 }
365
366 ci = d_inode(dir)->i_crypt_info;
367 if (ci && ci->ci_keyring_key &&
368 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
369 (1 << KEY_FLAG_REVOKED) |
370 (1 << KEY_FLAG_DEAD))))
371 ci = NULL;
372
373 /* this should eventually be an flag in d_flags */
374 spin_lock(&dentry->d_lock);
375 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
376 spin_unlock(&dentry->d_lock);
377 dir_has_key = (ci != NULL);
378 dput(dir);
379
380 /*
381 * If the dentry was cached without the key, and it is a
382 * negative dentry, it might be a valid name. We can't check
383 * if the key has since been made available due to locking
384 * reasons, so we fail the validation so ext4_lookup() can do
385 * this check.
386 *
387 * We also fail the validation if the dentry was created with
388 * the key present, but we no longer have the key, or vice versa.
389 */
390 if ((!cached_with_key && d_is_negative(dentry)) ||
391 (!cached_with_key && dir_has_key) ||
392 (cached_with_key && !dir_has_key))
393 return 0;
394 return 1;
395}
396
397const struct dentry_operations fscrypt_d_ops = {
398 .d_revalidate = fscrypt_d_revalidate,
399};
400EXPORT_SYMBOL(fscrypt_d_ops);
401
402/*
403 * Call fscrypt_decrypt_page on every single page, reusing the encryption
404 * context.
405 */
406static void completion_pages(struct work_struct *work)
407{
408 struct fscrypt_ctx *ctx =
409 container_of(work, struct fscrypt_ctx, r.work);
410 struct bio *bio = ctx->r.bio;
411 struct bio_vec *bv;
412 int i;
413
414 bio_for_each_segment_all(bv, bio, i) {
415 struct page *page = bv->bv_page;
416 int ret = fscrypt_decrypt_page(page);
417
418 if (ret) {
419 WARN_ON_ONCE(1);
420 SetPageError(page);
421 } else {
422 SetPageUptodate(page);
423 }
424 unlock_page(page);
425 }
426 fscrypt_release_ctx(ctx);
427 bio_put(bio);
428}
429
430void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
431{
432 INIT_WORK(&ctx->r.work, completion_pages);
433 ctx->r.bio = bio;
434 queue_work(fscrypt_read_workqueue, &ctx->r.work);
435}
436EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
437
438void fscrypt_pullback_bio_page(struct page **page, bool restore)
439{
440 struct fscrypt_ctx *ctx;
441 struct page *bounce_page;
442
443 /* The bounce data pages are unmapped. */
444 if ((*page)->mapping)
445 return;
446
447 /* The bounce data page is unmapped. */
448 bounce_page = *page;
449 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
450
451 /* restore control page */
452 *page = ctx->w.control_page;
453
454 if (restore)
455 fscrypt_restore_control_page(bounce_page);
456}
457EXPORT_SYMBOL(fscrypt_pullback_bio_page);
458
459void fscrypt_restore_control_page(struct page *page)
460{
461 struct fscrypt_ctx *ctx;
462
463 ctx = (struct fscrypt_ctx *)page_private(page);
464 set_page_private(page, (unsigned long)NULL);
465 ClearPagePrivate(page);
466 unlock_page(page);
467 fscrypt_release_ctx(ctx);
468}
469EXPORT_SYMBOL(fscrypt_restore_control_page);
470
471static void fscrypt_destroy(void)
472{
473 struct fscrypt_ctx *pos, *n;
474
475 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
476 kmem_cache_free(fscrypt_ctx_cachep, pos);
477 INIT_LIST_HEAD(&fscrypt_free_ctxs);
478 mempool_destroy(fscrypt_bounce_page_pool);
479 fscrypt_bounce_page_pool = NULL;
480}
481
482/**
483 * fscrypt_initialize() - allocate major buffers for fs encryption.
484 *
485 * We only call this when we start accessing encrypted files, since it
486 * results in memory getting allocated that wouldn't otherwise be used.
487 *
488 * Return: Zero on success, non-zero otherwise.
489 */
490int fscrypt_initialize(void)
491{
492 int i, res = -ENOMEM;
493
494 if (fscrypt_bounce_page_pool)
495 return 0;
496
497 mutex_lock(&fscrypt_init_mutex);
498 if (fscrypt_bounce_page_pool)
499 goto already_initialized;
500
501 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
502 struct fscrypt_ctx *ctx;
503
504 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
505 if (!ctx)
506 goto fail;
507 list_add(&ctx->free_list, &fscrypt_free_ctxs);
508 }
509
510 fscrypt_bounce_page_pool =
511 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
512 if (!fscrypt_bounce_page_pool)
513 goto fail;
514
515already_initialized:
516 mutex_unlock(&fscrypt_init_mutex);
517 return 0;
518fail:
519 fscrypt_destroy();
520 mutex_unlock(&fscrypt_init_mutex);
521 return res;
522}
523EXPORT_SYMBOL(fscrypt_initialize);
524
525/**
526 * fscrypt_init() - Set up for fs encryption.
527 */
528static int __init fscrypt_init(void)
529{
530 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
531 WQ_HIGHPRI, 0);
532 if (!fscrypt_read_workqueue)
533 goto fail;
534
535 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
536 if (!fscrypt_ctx_cachep)
537 goto fail_free_queue;
538
539 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
540 if (!fscrypt_info_cachep)
541 goto fail_free_ctx;
542
543 return 0;
544
545fail_free_ctx:
546 kmem_cache_destroy(fscrypt_ctx_cachep);
547fail_free_queue:
548 destroy_workqueue(fscrypt_read_workqueue);
549fail:
550 return -ENOMEM;
551}
552module_init(fscrypt_init)
553
554/**
555 * fscrypt_exit() - Shutdown the fs encryption system
556 */
557static void __exit fscrypt_exit(void)
558{
559 fscrypt_destroy();
560
561 if (fscrypt_read_workqueue)
562 destroy_workqueue(fscrypt_read_workqueue);
563 kmem_cache_destroy(fscrypt_ctx_cachep);
564 kmem_cache_destroy(fscrypt_info_cachep);
565}
566module_exit(fscrypt_exit);
567
568MODULE_LICENSE("GPL");