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