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 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
  45                                               pgoff_t lblk, sector_t pblk,
  46                                               unsigned int len)
  47 {
  48         const unsigned int blockbits = inode->i_blkbits;
  49         const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
  50         struct bio *bio;
  51         int ret, err = 0;
  52         int num_pages = 0;
  53
  54         /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
  55         bio = bio_alloc(GFP_NOFS, BIO_MAX_PAGES);
  56
  57         while (len) {
  58                 unsigned int blocks_this_page = min(len, blocks_per_page);
  59                 unsigned int bytes_this_page = blocks_this_page << blockbits;
  60
  61                 if (num_pages == 0) {
  62                         fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
  63                         bio_set_dev(bio, inode->i_sb->s_bdev);
  64                         bio->bi_iter.bi_sector =
  65                                         pblk << (blockbits - SECTOR_SHIFT);
  66                         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
  67                 }
  68                 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
  69                 if (WARN_ON(ret != bytes_this_page)) {
  70                         err = -EIO;
  71                         goto out;
  72                 }
  73                 num_pages++;
  74                 len -= blocks_this_page;
  75                 lblk += blocks_this_page;
  76                 pblk += blocks_this_page;
  77                 if (num_pages == BIO_MAX_PAGES || !len ||
  78                     !fscrypt_mergeable_bio(bio, inode, lblk)) {
  79                         err = submit_bio_wait(bio);
  80                         if (err)
  81                                 goto out;
  82                         bio_reset(bio);
  83                         num_pages = 0;
  84                 }
  85         }
  86 out:
  87         bio_put(bio);
  88         return err;
  89 }
  90
  91 /**
  92  * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
  93  * @inode: the file's inode
  94  * @lblk: the first file logical block to zero out
  95  * @pblk: the first filesystem physical block to zero out
  96  * @len: number of blocks to zero out
  97  *
  98  * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
  99  * ciphertext blocks which decrypt to the all-zeroes block.  The blocks must be
 100  * both logically and physically contiguous.  It's also assumed that the
 101  * filesystem only uses a single block device, ->s_bdev.
 102  *
 103  * Note that since each block uses a different IV, this involves writing a
 104  * different ciphertext to each block; we can't simply reuse the same one.
 105  *
 106  * Return: 0 on success; -errno on failure.
 107  */
 108 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 109                           sector_t pblk, unsigned int len)
 110 {
 111         const unsigned int blockbits = inode->i_blkbits;
 112         const unsigned int blocksize = 1 << blockbits;
 113         const unsigned int blocks_per_page_bits = PAGE_SHIFT - blockbits;
 114         const unsigned int blocks_per_page = 1 << blocks_per_page_bits;
 115         struct page *pages[16]; /* write up to 16 pages at a time */
 116         unsigned int nr_pages;
 117         unsigned int i;
 118         unsigned int offset;
 119         struct bio *bio;
 120         int ret, err;
 121
 122         if (len == 0)
 123                 return 0;
 124
 125         if (fscrypt_inode_uses_inline_crypto(inode))
 126                 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
 127                                                           len);
 128
 129         BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_PAGES);
 130         nr_pages = min_t(unsigned int, ARRAY_SIZE(pages),
 131                          (len + blocks_per_page - 1) >> blocks_per_page_bits);
 132
 133         /*
 134          * We need at least one page for ciphertext.  Allocate the first one
 135          * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
 136          *
 137          * Any additional page allocations are allowed to fail, as they only
 138          * help performance, and waiting on the mempool for them could deadlock.
 139          */
 140         for (i = 0; i < nr_pages; i++) {
 141                 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
 142                                                      GFP_NOWAIT | __GFP_NOWARN);
 143                 if (!pages[i])
 144                         break;
 145         }
 146         nr_pages = i;
 147         if (WARN_ON(nr_pages <= 0))
 148                 return -EINVAL;
 149
 150         /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
 151         bio = bio_alloc(GFP_NOFS, nr_pages);
 152
 153         do {
 154                 bio_set_dev(bio, inode->i_sb->s_bdev);
 155                 bio->bi_iter.bi_sector = pblk << (blockbits - 9);
 156                 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 157
 158                 i = 0;
 159                 offset = 0;
 160                 do {
 161                         err = fscrypt_crypt_block(inode, FS_ENCRYPT, lblk,
 162                                                   ZERO_PAGE(0), pages[i],
 163                                                   blocksize, offset, GFP_NOFS);
 164                         if (err)
 165                                 goto out;
 166                         lblk++;
 167                         pblk++;
 168                         len--;
 169                         offset += blocksize;
 170                         if (offset == PAGE_SIZE || len == 0) {
 171                                 ret = bio_add_page(bio, pages[i++], offset, 0);
 172                                 if (WARN_ON(ret != offset)) {
 173                                         err = -EIO;
 174                                         goto out;
 175                                 }
 176                                 offset = 0;
 177                         }
 178                 } while (i != nr_pages && len != 0);
 179
 180                 err = submit_bio_wait(bio);
 181                 if (err)
 182                         goto out;
 183                 bio_reset(bio);
 184         } while (len != 0);
 185         err = 0;
 186 out:
 187         bio_put(bio);
 188         for (i = 0; i < nr_pages; i++)
 189                 fscrypt_free_bounce_page(pages[i]);
 190         return err;
 191 }
 192 EXPORT_SYMBOL(fscrypt_zeroout_range);