fs/crypto/bio.c

   1 // SPDX-License-Identifier: GPL-2.0
   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/module.h>
  25 #include <linux/bio.h>
  26 #include <linux/namei.h>
  27 #include "fscrypt_private.h"
  28
  29 void fscrypt_decrypt_bio(struct bio *bio)
  30 {
  31         struct bio_vec *bv;
  32         struct bvec_iter_all iter_all;
  33
  34         bio_for_each_segment_all(bv, bio, iter_all) {
  35                 struct page *page = bv->bv_page;
  36                 int ret = fscrypt_decrypt_pagecache_blocks(page, bv->bv_len,
  37                                                            bv->bv_offset);
  38                 if (ret)
  39                         SetPageError(page);
  40         }
  41 }
  42 EXPORT_SYMBOL(fscrypt_decrypt_bio);
  43
  44 /**
  45  * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
  46  * @inode: the file's inode
  47  * @lblk: the first file logical block to zero out
  48  * @pblk: the first filesystem physical block to zero out
  49  * @len: number of blocks to zero out
  50  *
  51  * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
  52  * ciphertext blocks which decrypt to the all-zeroes block.  The blocks must be
  53  * both logically and physically contiguous.  It's also assumed that the
  54  * filesystem only uses a single block device, ->s_bdev.
  55  *
  56  * Note that since each block uses a different IV, this involves writing a
  57  * different ciphertext to each block; we can't simply reuse the same one.
  58  *
  59  * Return: 0 on success; -errno on failure.
  60  */
  61 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
  62                           sector_t pblk, unsigned int len)
  63 {
  64         const unsigned int blockbits = inode->i_blkbits;
  65         const unsigned int blocksize = 1 << blockbits;
  66         const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
  67         const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
  68         struct page *pages[16]; /* write up to 16 pages at a time */
  69         unsigned int nr_pages;
  70         unsigned int i;
  71         unsigned int offset;
  72         struct bio *bio;
  73         int ret, err;
  74
  75         if (len == 0)
  76                 return 0;
  77
  78         BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_PAGES);
  79         nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
  80                          (len + blocks_per_page - 1) >> blocks_per_page_bits);
  81
  82         /*
  83          * We need at least one page for ciphertext.  Allocate the first one
  84          * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
  85          *
  86          * Any additional page allocations are allowed to fail, as they only
  87          * help performance, and waiting on the mempool for them could deadlock.
  88          */
  89         for (i = 0; i < nr_pages; i++) {
  90                 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
  91                                                      GFP_NOWAIT | __GFP_NOWARN);
  92                 if (!pages[i])
  93                         break;
  94         }
  95         nr_pages = i;
  96         if (WARN_ON(nr_pages <= 0))
  97                 return -EINVAL;
  98
  99         /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
 100         bio = bio_alloc(GFP_NOFS, nr_pages);
 101
 102         do {
 103                 bio_set_dev(bio, inode->i_sb->s_bdev);
 104                 bio->bi_iter.bi_sector = pblk << (blockbits - 9);
 105                 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 106
 107                 i = 0;
 108                 offset = 0;
 109                 do {
 110                         err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
 111                                                   ZERO_PAGE(0), pages[i],
 112                                                   blocksize, offset, GFP_NOFS);
 113                         if (err)
 114                                 goto out;
 115                         lblk++;
 116                         pblk++;
 117                         len--;
 118                         offset += blocksize;
 119                         if (offset == PAGE_SIZE || len == 0) {
 120                                 ret = bio_add_page(bio, pages[i++], offset, 0);
 121                                 if (WARN_ON(ret != offset)) {
 122                                         err = -EIO;
 123                                         goto out;
 124                                 }
 125                                 offset = 0;
 126                         }
 127                 } while (i != nr_pages && len != 0);
 128
 129                 err = submit_bio_wait(bio);
 130                 if (err)
 131                         goto out;
 132                 bio_reset(bio);
 133         } while (len != 0);
 134         err = 0;
 135 out:
 136         bio_put(bio);
 137         for (i = 0; i < nr_pages; i++)
 138                 fscrypt_free_bounce_page(pages[i]);
 139         return err;
 140 }
 141 EXPORT_SYMBOL(fscrypt_zeroout_range);