linux/fs/crypto/crypto.c
Eric Biggers 51e4e3153e fscrypt: support decrypting data from large folios
Try to make the filesystem-level decryption functions in fs/crypto/
aware of large folios.  This includes making fscrypt_decrypt_bio()
support the case where the bio contains large folios, and making
fscrypt_decrypt_pagecache_blocks() take a folio instead of a page.

There's no way to actually test this with large folios yet, but I've
tested that this doesn't cause any regressions.

Note that this patch just handles *decryption*, not encryption which
will be a little more difficult.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Link: https://lore.kernel.org/r/20230127224202.355629-1-ebiggers@kernel.org
2023-01-28 15:10:12 -08:00

407 lines
13 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* This contains encryption functions for per-file encryption.
*
* Copyright (C) 2015, Google, Inc.
* Copyright (C) 2015, Motorola Mobility
*
* Written by Michael Halcrow, 2014.
*
* Filename encryption additions
* Uday Savagaonkar, 2014
* Encryption policy handling additions
* Ildar Muslukhov, 2014
* Add fscrypt_pullback_bio_page()
* Jaegeuk Kim, 2015.
*
* This has not yet undergone a rigorous security audit.
*
* The usage of AES-XTS should conform to recommendations in NIST
* Special Publication 800-38E and IEEE P1619/D16.
*/
#include <linux/pagemap.h>
#include <linux/mempool.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <linux/ratelimit.h>
#include <crypto/skcipher.h>
#include "fscrypt_private.h"
static unsigned int num_prealloc_crypto_pages = 32;
module_param(num_prealloc_crypto_pages, uint, 0444);
MODULE_PARM_DESC(num_prealloc_crypto_pages,
"Number of crypto pages to preallocate");
static mempool_t *fscrypt_bounce_page_pool = NULL;
static struct workqueue_struct *fscrypt_read_workqueue;
static DEFINE_MUTEX(fscrypt_init_mutex);
struct kmem_cache *fscrypt_info_cachep;
void fscrypt_enqueue_decrypt_work(struct work_struct *work)
{
queue_work(fscrypt_read_workqueue, work);
}
EXPORT_SYMBOL(fscrypt_enqueue_decrypt_work);
struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags)
{
return mempool_alloc(fscrypt_bounce_page_pool, gfp_flags);
}
/**
* fscrypt_free_bounce_page() - free a ciphertext bounce page
* @bounce_page: the bounce page to free, or NULL
*
* Free a bounce page that was allocated by fscrypt_encrypt_pagecache_blocks(),
* or by fscrypt_alloc_bounce_page() directly.
*/
void fscrypt_free_bounce_page(struct page *bounce_page)
{
if (!bounce_page)
return;
set_page_private(bounce_page, (unsigned long)NULL);
ClearPagePrivate(bounce_page);
mempool_free(bounce_page, fscrypt_bounce_page_pool);
}
EXPORT_SYMBOL(fscrypt_free_bounce_page);
/*
* Generate the IV for the given logical block number within the given file.
* For filenames encryption, lblk_num == 0.
*
* Keep this in sync with fscrypt_limit_io_blocks(). fscrypt_limit_io_blocks()
* needs to know about any IV generation methods where the low bits of IV don't
* simply contain the lblk_num (e.g., IV_INO_LBLK_32).
*/
void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
const struct fscrypt_info *ci)
{
u8 flags = fscrypt_policy_flags(&ci->ci_policy);
memset(iv, 0, ci->ci_mode->ivsize);
if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) {
WARN_ON_ONCE(lblk_num > U32_MAX);
WARN_ON_ONCE(ci->ci_inode->i_ino > U32_MAX);
lblk_num |= (u64)ci->ci_inode->i_ino << 32;
} else if (flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) {
WARN_ON_ONCE(lblk_num > U32_MAX);
lblk_num = (u32)(ci->ci_hashed_ino + lblk_num);
} else if (flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) {
memcpy(iv->nonce, ci->ci_nonce, FSCRYPT_FILE_NONCE_SIZE);
}
iv->lblk_num = cpu_to_le64(lblk_num);
}
/* Encrypt or decrypt a single filesystem block of file contents */
int fscrypt_crypt_block(const struct inode *inode, fscrypt_direction_t rw,
u64 lblk_num, struct page *src_page,
struct page *dest_page, unsigned int len,
unsigned int offs, gfp_t gfp_flags)
{
union fscrypt_iv iv;
struct skcipher_request *req = NULL;
DECLARE_CRYPTO_WAIT(wait);
struct scatterlist dst, src;
struct fscrypt_info *ci = inode->i_crypt_info;
struct crypto_skcipher *tfm = ci->ci_enc_key.tfm;
int res = 0;
if (WARN_ON_ONCE(len <= 0))
return -EINVAL;
if (WARN_ON_ONCE(len % FSCRYPT_CONTENTS_ALIGNMENT != 0))
return -EINVAL;
fscrypt_generate_iv(&iv, lblk_num, ci);
req = skcipher_request_alloc(tfm, gfp_flags);
if (!req)
return -ENOMEM;
skcipher_request_set_callback(
req, CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
crypto_req_done, &wait);
sg_init_table(&dst, 1);
sg_set_page(&dst, dest_page, len, offs);
sg_init_table(&src, 1);
sg_set_page(&src, src_page, len, offs);
skcipher_request_set_crypt(req, &src, &dst, len, &iv);
if (rw == FS_DECRYPT)
res = crypto_wait_req(crypto_skcipher_decrypt(req), &wait);
else
res = crypto_wait_req(crypto_skcipher_encrypt(req), &wait);
skcipher_request_free(req);
if (res) {
fscrypt_err(inode, "%scryption failed for block %llu: %d",
(rw == FS_DECRYPT ? "De" : "En"), lblk_num, res);
return res;
}
return 0;
}
/**
* fscrypt_encrypt_pagecache_blocks() - Encrypt filesystem blocks from a
* pagecache page
* @page: The locked pagecache page containing the block(s) to encrypt
* @len: Total size of the block(s) to encrypt. Must be a nonzero
* multiple of the filesystem's block size.
* @offs: Byte offset within @page of the first block to encrypt. Must be
* a multiple of the filesystem's block size.
* @gfp_flags: Memory allocation flags. See details below.
*
* A new bounce page is allocated, and the specified block(s) are encrypted into
* it. In the bounce page, the ciphertext block(s) will be located at the same
* offsets at which the plaintext block(s) were located in the source page; any
* other parts of the bounce page will be left uninitialized. However, normally
* blocksize == PAGE_SIZE and the whole page is encrypted at once.
*
* This is for use by the filesystem's ->writepages() method.
*
* The bounce page allocation is mempool-backed, so it will always succeed when
* @gfp_flags includes __GFP_DIRECT_RECLAIM, e.g. when it's GFP_NOFS. However,
* only the first page of each bio can be allocated this way. To prevent
* deadlocks, for any additional pages a mask like GFP_NOWAIT must be used.
*
* Return: the new encrypted bounce page on success; an ERR_PTR() on failure
*/
struct page *fscrypt_encrypt_pagecache_blocks(struct page *page,
unsigned int len,
unsigned int offs,
gfp_t gfp_flags)
{
const struct inode *inode = page->mapping->host;
const unsigned int blockbits = inode->i_blkbits;
const unsigned int blocksize = 1 << blockbits;
struct page *ciphertext_page;
u64 lblk_num = ((u64)page->index << (PAGE_SHIFT - blockbits)) +
(offs >> blockbits);
unsigned int i;
int err;
if (WARN_ON_ONCE(!PageLocked(page)))
return ERR_PTR(-EINVAL);
if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
return ERR_PTR(-EINVAL);
ciphertext_page = fscrypt_alloc_bounce_page(gfp_flags);
if (!ciphertext_page)
return ERR_PTR(-ENOMEM);
for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num,
page, ciphertext_page,
blocksize, i, gfp_flags);
if (err) {
fscrypt_free_bounce_page(ciphertext_page);
return ERR_PTR(err);
}
}
SetPagePrivate(ciphertext_page);
set_page_private(ciphertext_page, (unsigned long)page);
return ciphertext_page;
}
EXPORT_SYMBOL(fscrypt_encrypt_pagecache_blocks);
/**
* fscrypt_encrypt_block_inplace() - Encrypt a filesystem block in-place
* @inode: The inode to which this block belongs
* @page: The page containing the block to encrypt
* @len: Size of block to encrypt. This must be a multiple of
* FSCRYPT_CONTENTS_ALIGNMENT.
* @offs: Byte offset within @page at which the block to encrypt begins
* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
* number of the block within the file
* @gfp_flags: Memory allocation flags
*
* Encrypt a possibly-compressed filesystem block that is located in an
* arbitrary page, not necessarily in the original pagecache page. The @inode
* and @lblk_num must be specified, as they can't be determined from @page.
*
* Return: 0 on success; -errno on failure
*/
int fscrypt_encrypt_block_inplace(const struct inode *inode, struct page *page,
unsigned int len, unsigned int offs,
u64 lblk_num, gfp_t gfp_flags)
{
return fscrypt_crypt_block(inode, FS_ENCRYPT, lblk_num, page, page,
len, offs, gfp_flags);
}
EXPORT_SYMBOL(fscrypt_encrypt_block_inplace);
/**
* fscrypt_decrypt_pagecache_blocks() - Decrypt filesystem blocks in a
* pagecache folio
* @folio: The locked pagecache folio containing the block(s) to decrypt
* @len: Total size of the block(s) to decrypt. Must be a nonzero
* multiple of the filesystem's block size.
* @offs: Byte offset within @folio of the first block to decrypt. Must be
* a multiple of the filesystem's block size.
*
* The specified block(s) are decrypted in-place within the pagecache folio,
* which must still be locked and not uptodate.
*
* This is for use by the filesystem's ->readahead() method.
*
* Return: 0 on success; -errno on failure
*/
int fscrypt_decrypt_pagecache_blocks(struct folio *folio, size_t len,
size_t offs)
{
const struct inode *inode = folio->mapping->host;
const unsigned int blockbits = inode->i_blkbits;
const unsigned int blocksize = 1 << blockbits;
u64 lblk_num = ((u64)folio->index << (PAGE_SHIFT - blockbits)) +
(offs >> blockbits);
size_t i;
int err;
if (WARN_ON_ONCE(!folio_test_locked(folio)))
return -EINVAL;
if (WARN_ON_ONCE(len <= 0 || !IS_ALIGNED(len | offs, blocksize)))
return -EINVAL;
for (i = offs; i < offs + len; i += blocksize, lblk_num++) {
struct page *page = folio_page(folio, i >> PAGE_SHIFT);
err = fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page,
page, blocksize, i & ~PAGE_MASK,
GFP_NOFS);
if (err)
return err;
}
return 0;
}
EXPORT_SYMBOL(fscrypt_decrypt_pagecache_blocks);
/**
* fscrypt_decrypt_block_inplace() - Decrypt a filesystem block in-place
* @inode: The inode to which this block belongs
* @page: The page containing the block to decrypt
* @len: Size of block to decrypt. This must be a multiple of
* FSCRYPT_CONTENTS_ALIGNMENT.
* @offs: Byte offset within @page at which the block to decrypt begins
* @lblk_num: Filesystem logical block number of the block, i.e. the 0-based
* number of the block within the file
*
* Decrypt a possibly-compressed filesystem block that is located in an
* arbitrary page, not necessarily in the original pagecache page. The @inode
* and @lblk_num must be specified, as they can't be determined from @page.
*
* Return: 0 on success; -errno on failure
*/
int fscrypt_decrypt_block_inplace(const struct inode *inode, struct page *page,
unsigned int len, unsigned int offs,
u64 lblk_num)
{
return fscrypt_crypt_block(inode, FS_DECRYPT, lblk_num, page, page,
len, offs, GFP_NOFS);
}
EXPORT_SYMBOL(fscrypt_decrypt_block_inplace);
/**
* fscrypt_initialize() - allocate major buffers for fs encryption.
* @cop_flags: fscrypt operations flags
*
* We only call this when we start accessing encrypted files, since it
* results in memory getting allocated that wouldn't otherwise be used.
*
* Return: 0 on success; -errno on failure
*/
int fscrypt_initialize(unsigned int cop_flags)
{
int err = 0;
/* No need to allocate a bounce page pool if this FS won't use it. */
if (cop_flags & FS_CFLG_OWN_PAGES)
return 0;
mutex_lock(&fscrypt_init_mutex);
if (fscrypt_bounce_page_pool)
goto out_unlock;
err = -ENOMEM;
fscrypt_bounce_page_pool =
mempool_create_page_pool(num_prealloc_crypto_pages, 0);
if (!fscrypt_bounce_page_pool)
goto out_unlock;
err = 0;
out_unlock:
mutex_unlock(&fscrypt_init_mutex);
return err;
}
void fscrypt_msg(const struct inode *inode, const char *level,
const char *fmt, ...)
{
static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
DEFAULT_RATELIMIT_BURST);
struct va_format vaf;
va_list args;
if (!__ratelimit(&rs))
return;
va_start(args, fmt);
vaf.fmt = fmt;
vaf.va = &args;
if (inode && inode->i_ino)
printk("%sfscrypt (%s, inode %lu): %pV\n",
level, inode->i_sb->s_id, inode->i_ino, &vaf);
else if (inode)
printk("%sfscrypt (%s): %pV\n", level, inode->i_sb->s_id, &vaf);
else
printk("%sfscrypt: %pV\n", level, &vaf);
va_end(args);
}
/**
* fscrypt_init() - Set up for fs encryption.
*
* Return: 0 on success; -errno on failure
*/
static int __init fscrypt_init(void)
{
int err = -ENOMEM;
/*
* Use an unbound workqueue to allow bios to be decrypted in parallel
* even when they happen to complete on the same CPU. This sacrifices
* locality, but it's worthwhile since decryption is CPU-intensive.
*
* Also use a high-priority workqueue to prioritize decryption work,
* which blocks reads from completing, over regular application tasks.
*/
fscrypt_read_workqueue = alloc_workqueue("fscrypt_read_queue",
WQ_UNBOUND | WQ_HIGHPRI,
num_online_cpus());
if (!fscrypt_read_workqueue)
goto fail;
fscrypt_info_cachep = KMEM_CACHE(fscrypt_info, SLAB_RECLAIM_ACCOUNT);
if (!fscrypt_info_cachep)
goto fail_free_queue;
err = fscrypt_init_keyring();
if (err)
goto fail_free_info;
return 0;
fail_free_info:
kmem_cache_destroy(fscrypt_info_cachep);
fail_free_queue:
destroy_workqueue(fscrypt_read_workqueue);
fail:
return err;
}
late_initcall(fscrypt_init)