fs/crypto/bio.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Utility functions for file contents encryption/decryption on
   4  * block device-based filesystems.
   5  *
   6  * Copyright (C) 2015, Google, Inc.
   7  * Copyright (C) 2015, Motorola Mobility
   8  */
   9
  10 #include <linux/pagemap.h>
  11 #include <linux/module.h>
  12 #include <linux/bio.h>
  13 #include <linux/namei.h>
  14 #include "fscrypt_private.h"
  15
  16 /**
  17  * fscrypt_decrypt_bio() - decrypt the contents of a bio
  18  * @bio: the bio to decrypt
  19  *
  20  * Decrypt the contents of a "read" bio following successful completion of the
  21  * underlying disk read.  The bio must be reading a whole number of blocks of an
  22  * encrypted file directly into the page cache.  If the bio is reading the
  23  * ciphertext into bounce pages instead of the page cache (for example, because
  24  * the file is also compressed, so decompression is required after decryption),
  25  * then this function isn't applicable.  This function may sleep, so it must be
  26  * called from a workqueue rather than from the bio's bi_end_io callback.
  27  *
  28  * Return: %true on success; %false on failure.  On failure, bio->bi_status is
  29  *         also set to an error status.
  30  */
  31 bool fscrypt_decrypt_bio(struct bio *bio)
  32 {
  33         struct folio_iter fi;
  34
  35         bio_for_each_folio_all(fi, bio) {
  36                 int err = fscrypt_decrypt_pagecache_blocks(fi.folio, fi.length,
  37                                                            fi.offset);
  38
  39                 if (err) {
  40                         bio->bi_status = errno_to_blk_status(err);
  41                         return false;
  42                 }
  43         }
  44         return true;
  45 }
  46 EXPORT_SYMBOL(fscrypt_decrypt_bio);
  47
  48 static int fscrypt_zeroout_range_inline_crypt(const struct inode *inode,
  49                                               pgoff_t lblk, sector_t pblk,
  50                                               unsigned int len)
  51 {
  52         const unsigned int blockbits = inode->i_blkbits;
  53         const unsigned int blocks_per_page = 1 << (PAGE_SHIFT - blockbits);
  54         struct bio *bio;
  55         int ret, err = 0;
  56         int num_pages = 0;
  57
  58         /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
  59         bio = bio_alloc(inode->i_sb->s_bdev, BIO_MAX_VECS, REQ_OP_WRITE,
  60                         GFP_NOFS);
  61
  62         while (len) {
  63                 unsigned int blocks_this_page = min(len, blocks_per_page);
  64                 unsigned int bytes_this_page = blocks_this_page << blockbits;
  65
  66                 if (num_pages == 0) {
  67                         fscrypt_set_bio_crypt_ctx(bio, inode, lblk, GFP_NOFS);
  68                         bio->bi_iter.bi_sector =
  69                                         pblk << (blockbits - SECTOR_SHIFT);
  70                 }
  71                 ret = bio_add_page(bio, ZERO_PAGE(0), bytes_this_page, 0);
  72                 if (WARN_ON_ONCE(ret != bytes_this_page)) {
  73                         err = -EIO;
  74                         goto out;
  75                 }
  76                 num_pages++;
  77                 len -= blocks_this_page;
  78                 lblk += blocks_this_page;
  79                 pblk += blocks_this_page;
  80                 if (num_pages == BIO_MAX_VECS || !len ||
  81                     !fscrypt_mergeable_bio(bio, inode, lblk)) {
  82                         err = submit_bio_wait(bio);
  83                         if (err)
  84                                 goto out;
  85                         bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
  86                         num_pages = 0;
  87                 }
  88         }
  89 out:
  90         bio_put(bio);
  91         return err;
  92 }
  93
  94 /**
  95  * fscrypt_zeroout_range() - zero out a range of blocks in an encrypted file
  96  * @inode: the file's inode
  97  * @lblk: the first file logical block to zero out
  98  * @pblk: the first filesystem physical block to zero out
  99  * @len: number of blocks to zero out
 100  *
 101  * Zero out filesystem blocks in an encrypted regular file on-disk, i.e. write
 102  * ciphertext blocks which decrypt to the all-zeroes block.  The blocks must be
 103  * both logically and physically contiguous.  It's also assumed that the
 104  * filesystem only uses a single block device, ->s_bdev.
 105  *
 106  * Note that since each block uses a different IV, this involves writing a
 107  * different ciphertext to each block; we can't simply reuse the same one.
 108  *
 109  * Return: 0 on success; -errno on failure.
 110  */
 111 int fscrypt_zeroout_range(const struct inode *inode, pgoff_t lblk,
 112                           sector_t pblk, unsigned int len)
 113 {
 114         const struct fscrypt_inode_info *ci = inode->i_crypt_info;
 115         const unsigned int du_bits = ci->ci_data_unit_bits;
 116         const unsigned int du_size = 1U << du_bits;
 117         const unsigned int du_per_page_bits = PAGE_SHIFT - du_bits;
 118         const unsigned int du_per_page = 1U << du_per_page_bits;
 119         u64 du_index = (u64)lblk << (inode->i_blkbits - du_bits);
 120         u64 du_remaining = (u64)len << (inode->i_blkbits - du_bits);
 121         sector_t sector = pblk << (inode->i_blkbits - SECTOR_SHIFT);
 122         struct page *pages[16]; /* write up to 16 pages at a time */
 123         unsigned int nr_pages;
 124         unsigned int i;
 125         unsigned int offset;
 126         struct bio *bio;
 127         int ret, err;
 128
 129         if (len == 0)
 130                 return 0;
 131
 132         if (fscrypt_inode_uses_inline_crypto(inode))
 133                 return fscrypt_zeroout_range_inline_crypt(inode, lblk, pblk,
 134                                                           len);
 135
 136         BUILD_BUG_ON(ARRAY_SIZE(pages) > BIO_MAX_VECS);
 137         nr_pages = min_t(u64, ARRAY_SIZE(pages),
 138                          (du_remaining + du_per_page - 1) >> du_per_page_bits);
 139
 140         /*
 141          * We need at least one page for ciphertext.  Allocate the first one
 142          * from a mempool, with __GFP_DIRECT_RECLAIM set so that it can't fail.
 143          *
 144          * Any additional page allocations are allowed to fail, as they only
 145          * help performance, and waiting on the mempool for them could deadlock.
 146          */
 147         for (i = 0; i < nr_pages; i++) {
 148                 pages[i] = fscrypt_alloc_bounce_page(i == 0 ? GFP_NOFS :
 149                                                      GFP_NOWAIT | __GFP_NOWARN);
 150                 if (!pages[i])
 151                         break;
 152         }
 153         nr_pages = i;
 154         if (WARN_ON_ONCE(nr_pages <= 0))
 155                 return -EINVAL;
 156
 157         /* This always succeeds since __GFP_DIRECT_RECLAIM is set. */
 158         bio = bio_alloc(inode->i_sb->s_bdev, nr_pages, REQ_OP_WRITE, GFP_NOFS);
 159
 160         do {
 161                 bio->bi_iter.bi_sector = sector;
 162
 163                 i = 0;
 164                 offset = 0;
 165                 do {
 166                         err = fscrypt_crypt_data_unit(ci, FS_ENCRYPT, du_index,
 167                                                       ZERO_PAGE(0), pages[i],
 168                                                       du_size, offset,
 169                                                       GFP_NOFS);
 170                         if (err)
 171                                 goto out;
 172                         du_index++;
 173                         sector += 1U << (du_bits - SECTOR_SHIFT);
 174                         du_remaining--;
 175                         offset += du_size;
 176                         if (offset == PAGE_SIZE || du_remaining == 0) {
 177                                 ret = bio_add_page(bio, pages[i++], offset, 0);
 178                                 if (WARN_ON_ONCE(ret != offset)) {
 179                                         err = -EIO;
 180                                         goto out;
 181                                 }
 182                                 offset = 0;
 183                         }
 184                 } while (i != nr_pages && du_remaining != 0);
 185
 186                 err = submit_bio_wait(bio);
 187                 if (err)
 188                         goto out;
 189                 bio_reset(bio, inode->i_sb->s_bdev, REQ_OP_WRITE);
 190         } while (du_remaining != 0);
 191         err = 0;
 192 out:
 193         bio_put(bio);
 194         for (i = 0; i < nr_pages; i++)
 195                 fscrypt_free_bounce_page(pages[i]);
 196         return err;
 197 }
 198 EXPORT_SYMBOL(fscrypt_zeroout_range);