2 * This contains encryption functions for per-file encryption.
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility
7 * Written by Michael Halcrow, 2014.
9 * Filename encryption additions
10 * Uday Savagaonkar, 2014
11 * Encryption policy handling additions
12 * Ildar Muslukhov, 2014
13 * Add fscrypt_pullback_bio_page()
16 * This has not yet undergone a rigorous security audit.
18 * The usage of AES-XTS should conform to recommendations in NIST
19 * Special Publication 800-38E and IEEE P1619/D16.
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"
32 static unsigned int num_prealloc_crypto_pages = 32;
33 static unsigned int num_prealloc_crypto_ctxs = 128;
35 module_param(num_prealloc_crypto_pages, uint, 0444);
36 MODULE_PARM_DESC(num_prealloc_crypto_pages,
37 "Number of crypto pages to preallocate");
38 module_param(num_prealloc_crypto_ctxs, uint, 0444);
39 MODULE_PARM_DESC(num_prealloc_crypto_ctxs,
40 "Number of crypto contexts to preallocate");
42 static mempool_t *fscrypt_bounce_page_pool = NULL;
44 static LIST_HEAD(fscrypt_free_ctxs);
45 static DEFINE_SPINLOCK(fscrypt_ctx_lock);
47 static struct workqueue_struct *fscrypt_read_workqueue;
48 static DEFINE_MUTEX(fscrypt_init_mutex);
50 static struct kmem_cache *fscrypt_ctx_cachep;
51 struct kmem_cache *fscrypt_info_cachep;
54 * fscrypt_release_ctx() - Releases an encryption context
55 * @ctx: The encryption context to release.
57 * If the encryption context was allocated from the pre-allocated pool, returns
58 * it to that pool. Else, frees it.
60 * If there's a bounce page in the context, this frees that.
62 void fscrypt_release_ctx(struct fscrypt_ctx *ctx)
66 if (ctx->flags & FS_WRITE_PATH_FL && ctx->w.bounce_page) {
67 mempool_free(ctx->w.bounce_page, fscrypt_bounce_page_pool);
68 ctx->w.bounce_page = NULL;
70 ctx->w.control_page = NULL;
71 if (ctx->flags & FS_CTX_REQUIRES_FREE_ENCRYPT_FL) {
72 kmem_cache_free(fscrypt_ctx_cachep, ctx);
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);
79 EXPORT_SYMBOL(fscrypt_release_ctx);
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
86 * Allocates and initializes an encryption context.
88 * Return: An allocated and initialized encryption context on success; error
89 * value or NULL otherwise.
91 struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode, gfp_t gfp_flags)
93 struct fscrypt_ctx *ctx = NULL;
94 struct fscrypt_info *ci = inode->i_crypt_info;
98 return ERR_PTR(-ENOKEY);
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.
110 spin_lock_irqsave(&fscrypt_ctx_lock, flags);
111 ctx = list_first_entry_or_null(&fscrypt_free_ctxs,
112 struct fscrypt_ctx, free_list);
114 list_del(&ctx->free_list);
115 spin_unlock_irqrestore(&fscrypt_ctx_lock, flags);
117 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, gfp_flags);
119 return ERR_PTR(-ENOMEM);
120 ctx->flags |= FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
122 ctx->flags &= ~FS_CTX_REQUIRES_FREE_ENCRYPT_FL;
124 ctx->flags &= ~FS_WRITE_PATH_FL;
127 EXPORT_SYMBOL(fscrypt_get_ctx);
130 * page_crypt_complete() - completion callback for page crypto
131 * @req: The asynchronous cipher request context
132 * @res: The result of the cipher operation
134 static void page_crypt_complete(struct crypto_async_request *req, int res)
136 struct fscrypt_completion_result *ecr = req->data;
138 if (res == -EINPROGRESS)
141 complete(&ecr->completion);
147 } fscrypt_direction_t;
149 static 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,
157 u8 padding[FS_XTS_TWEAK_SIZE - sizeof(__le64)];
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;
168 req = skcipher_request_alloc(tfm, gfp_flags);
170 printk_ratelimited(KERN_ERR
171 "%s: crypto_request_alloc() failed\n",
176 skcipher_request_set_callback(
177 req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
178 page_crypt_complete, &ecr);
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));
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);
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);
198 skcipher_request_free(req);
200 printk_ratelimited(KERN_ERR
201 "%s: crypto_skcipher_encrypt() returned %d\n",
208 static struct page *alloc_bounce_page(struct fscrypt_ctx *ctx, gfp_t gfp_flags)
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_WRITE_PATH_FL;
214 return ctx->w.bounce_page;
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
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
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.
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.
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
245 * Return: A page with the encrypted content on success. Else, an
246 * error value or NULL.
248 struct page *fscrypt_encrypt_page(const struct inode *inode,
252 u64 lblk_num, gfp_t gfp_flags)
255 struct fscrypt_ctx *ctx;
256 struct page *ciphertext_page = page;
259 BUG_ON(len % FS_CRYPTO_BLOCK_SIZE != 0);
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);
269 return ciphertext_page;
272 BUG_ON(!PageLocked(page));
274 ctx = fscrypt_get_ctx(inode, gfp_flags);
276 return (struct page *)ctx;
278 /* The encryption operation will require a bounce page. */
279 ciphertext_page = alloc_bounce_page(ctx, gfp_flags);
280 if (IS_ERR(ciphertext_page))
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);
288 ciphertext_page = ERR_PTR(err);
291 SetPagePrivate(ciphertext_page);
292 set_page_private(ciphertext_page, (unsigned long)ctx);
293 lock_page(ciphertext_page);
294 return ciphertext_page;
297 fscrypt_release_ctx(ctx);
298 return ciphertext_page;
300 EXPORT_SYMBOL(fscrypt_encrypt_page);
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.
311 * Decrypts page in-place using the ctx encryption context.
313 * Called from the read completion callback.
315 * Return: Zero on success, non-zero otherwise.
317 int fscrypt_decrypt_page(const struct inode *inode, struct page *page,
318 unsigned int len, unsigned int offs, u64 lblk_num)
320 if (!(inode->i_sb->s_cop->flags & FS_CFLG_OWN_PAGES))
321 BUG_ON(!PageLocked(page));
323 return do_page_crypto(inode, FS_DECRYPT, lblk_num, page, page, len,
326 EXPORT_SYMBOL(fscrypt_decrypt_page);
328 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
329 sector_t pblk, unsigned int len)
331 struct fscrypt_ctx *ctx;
332 struct page *ciphertext_page = NULL;
336 BUG_ON(inode->i_sb->s_blocksize != PAGE_SIZE);
338 ctx = fscrypt_get_ctx(inode, GFP_NOFS);
342 ciphertext_page = alloc_bounce_page(ctx, GFP_NOWAIT);
343 if (IS_ERR(ciphertext_page)) {
344 err = PTR_ERR(ciphertext_page);
349 err = do_page_crypto(inode, FS_ENCRYPT, lblk,
350 ZERO_PAGE(0), ciphertext_page,
351 PAGE_SIZE, 0, GFP_NOFS);
355 bio = bio_alloc(GFP_NOWAIT, 1);
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! */
373 err = submit_bio_wait(bio);
374 if ((err == 0) && bio->bi_error)
384 fscrypt_release_ctx(ctx);
387 EXPORT_SYMBOL(fscrypt_zeroout_range);
390 * Validate dentries for encrypted directories to make sure we aren't
391 * potentially caching stale data after a key has been added or
394 static int fscrypt_d_revalidate(struct dentry *dentry, unsigned int flags)
397 struct fscrypt_info *ci;
398 int dir_has_key, cached_with_key;
400 if (flags & LOOKUP_RCU)
403 dir = dget_parent(dentry);
404 if (!d_inode(dir)->i_sb->s_cop->is_encrypted(d_inode(dir))) {
409 ci = d_inode(dir)->i_crypt_info;
410 if (ci && ci->ci_keyring_key &&
411 (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
412 (1 << KEY_FLAG_REVOKED) |
413 (1 << KEY_FLAG_DEAD))))
416 /* this should eventually be an flag in d_flags */
417 spin_lock(&dentry->d_lock);
418 cached_with_key = dentry->d_flags & DCACHE_ENCRYPTED_WITH_KEY;
419 spin_unlock(&dentry->d_lock);
420 dir_has_key = (ci != NULL);
424 * If the dentry was cached without the key, and it is a
425 * negative dentry, it might be a valid name. We can't check
426 * if the key has since been made available due to locking
427 * reasons, so we fail the validation so ext4_lookup() can do
430 * We also fail the validation if the dentry was created with
431 * the key present, but we no longer have the key, or vice versa.
433 if ((!cached_with_key && d_is_negative(dentry)) ||
434 (!cached_with_key && dir_has_key) ||
435 (cached_with_key && !dir_has_key))
440 const struct dentry_operations fscrypt_d_ops = {
441 .d_revalidate = fscrypt_d_revalidate,
443 EXPORT_SYMBOL(fscrypt_d_ops);
446 * Call fscrypt_decrypt_page on every single page, reusing the encryption
449 static void completion_pages(struct work_struct *work)
451 struct fscrypt_ctx *ctx =
452 container_of(work, struct fscrypt_ctx, r.work);
453 struct bio *bio = ctx->r.bio;
457 bio_for_each_segment_all(bv, bio, i) {
458 struct page *page = bv->bv_page;
459 int ret = fscrypt_decrypt_page(page->mapping->host, page,
460 PAGE_SIZE, 0, page->index);
466 SetPageUptodate(page);
470 fscrypt_release_ctx(ctx);
474 void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *ctx, struct bio *bio)
476 INIT_WORK(&ctx->r.work, completion_pages);
478 queue_work(fscrypt_read_workqueue, &ctx->r.work);
480 EXPORT_SYMBOL(fscrypt_decrypt_bio_pages);
482 void fscrypt_pullback_bio_page(struct page **page, bool restore)
484 struct fscrypt_ctx *ctx;
485 struct page *bounce_page;
487 /* The bounce data pages are unmapped. */
488 if ((*page)->mapping)
491 /* The bounce data page is unmapped. */
493 ctx = (struct fscrypt_ctx *)page_private(bounce_page);
495 /* restore control page */
496 *page = ctx->w.control_page;
499 fscrypt_restore_control_page(bounce_page);
501 EXPORT_SYMBOL(fscrypt_pullback_bio_page);
503 void fscrypt_restore_control_page(struct page *page)
505 struct fscrypt_ctx *ctx;
507 ctx = (struct fscrypt_ctx *)page_private(page);
508 set_page_private(page, (unsigned long)NULL);
509 ClearPagePrivate(page);
511 fscrypt_release_ctx(ctx);
513 EXPORT_SYMBOL(fscrypt_restore_control_page);
515 static void fscrypt_destroy(void)
517 struct fscrypt_ctx *pos, *n;
519 list_for_each_entry_safe(pos, n, &fscrypt_free_ctxs, free_list)
520 kmem_cache_free(fscrypt_ctx_cachep, pos);
521 INIT_LIST_HEAD(&fscrypt_free_ctxs);
522 mempool_destroy(fscrypt_bounce_page_pool);
523 fscrypt_bounce_page_pool = NULL;
527 * fscrypt_initialize() - allocate major buffers for fs encryption.
529 * We only call this when we start accessing encrypted files, since it
530 * results in memory getting allocated that wouldn't otherwise be used.
532 * Return: Zero on success, non-zero otherwise.
534 int fscrypt_initialize(void)
536 int i, res = -ENOMEM;
538 if (fscrypt_bounce_page_pool)
541 mutex_lock(&fscrypt_init_mutex);
542 if (fscrypt_bounce_page_pool)
543 goto already_initialized;
545 for (i = 0; i < num_prealloc_crypto_ctxs; i++) {
546 struct fscrypt_ctx *ctx;
548 ctx = kmem_cache_zalloc(fscrypt_ctx_cachep, GFP_NOFS);
551 list_add(&ctx->free_list, &fscrypt_free_ctxs);
554 fscrypt_bounce_page_pool =
555 mempool_create_page_pool(num_prealloc_crypto_pages, 0);
556 if (!fscrypt_bounce_page_pool)
560 mutex_unlock(&fscrypt_init_mutex);
564 mutex_unlock(&fscrypt_init_mutex);
569 * fscrypt_init() - Set up for fs encryption.
571 static int __init fscrypt_init(void)
573 fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
575 if (!fscrypt_read_workqueue)
578 fscrypt_ctx_cachep = KMEM_CACHE(fscrypt_ctx, SLAB_RECLAIM_ACCOUNT);
579 if (!fscrypt_ctx_cachep)
580 goto fail_free_queue;
582 fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
583 if (!fscrypt_info_cachep)
589 kmem_cache_destroy(fscrypt_ctx_cachep);
591 destroy_workqueue(fscrypt_read_workqueue);
595 module_init(fscrypt_init)
598 * fscrypt_exit() - Shutdown the fs encryption system
600 static void __exit fscrypt_exit(void)
604 if (fscrypt_read_workqueue)
605 destroy_workqueue(fscrypt_read_workqueue);
606 kmem_cache_destroy(fscrypt_ctx_cachep);
607 kmem_cache_destroy(fscrypt_info_cachep);
609 module_exit(fscrypt_exit);
611 MODULE_LICENSE("GPL");