implement-the-ext4-decryption-read-path

   1 ext4 crypto: implement the ext4 decryption read path
   2
   3 From: Michael Halcrow <mhalcrow@google.com>
   4
   5 Signed-off-by: Michael Halcrow <mhalcrow@google.com>
   6 Signed-off-by: Ildar Muslukhov <ildarm@google.com>
   7 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   8 ---
   9  fs/ext4/file.c     | 18 ++++++++++++++--
  10  fs/ext4/inode.c    |  7 ++++++
  11  fs/ext4/readpage.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
  12  3 files changed, 88 insertions(+), 3 deletions(-)
  13
  14 diff --git a/fs/ext4/file.c b/fs/ext4/file.c
  15 index fcc6c13..b132a3c 100644
  16 --- a/fs/ext4/file.c
  17 +++ b/fs/ext4/file.c
  18 @@ -218,6 +218,13 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
  19
  20  static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
  21  {
  22 +       struct inode *inode = file->f_mapping->host;
  23 +
  24 +       if (ext4_encrypted_inode(inode)) {
  25 +               int err = ext4_generate_encryption_key(inode);
  26 +               if (err)
  27 +                       return 0;
  28 +       }
  29         file_accessed(file);
  30         if (IS_DAX(file_inode(file))) {
  31                 vma->vm_ops = &ext4_dax_vm_ops;
  32 @@ -235,6 +242,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
  33         struct vfsmount *mnt = filp->f_path.mnt;
  34         struct path path;
  35         char buf[64], *cp;
  36 +       int ret;
  37
  38         if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
  39                      !(sb->s_flags & MS_RDONLY))) {
  40 @@ -273,11 +281,17 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
  41          * writing and the journal is present
  42          */
  43         if (filp->f_mode & FMODE_WRITE) {
  44 -               int ret = ext4_inode_attach_jinode(inode);
  45 +               ret = ext4_inode_attach_jinode(inode);
  46                 if (ret < 0)
  47                         return ret;
  48         }
  49 -       return dquot_file_open(inode, filp);
  50 +       ret = dquot_file_open(inode, filp);
  51 +       if (!ret && ext4_encrypted_inode(inode)) {
  52 +               ret = ext4_generate_encryption_key(inode);
  53 +               if (ret)
  54 +                       ret = -EACCES;
  55 +       }
  56 +       return ret;
  57  }
  58
  59  /*
  60 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  61 index 7c4527e..8b4fe62 100644
  62 --- a/fs/ext4/inode.c
  63 +++ b/fs/ext4/inode.c
  64 @@ -3370,6 +3370,13 @@ static int __ext4_block_zero_page_range(handle_t *handle,
  65                 /* Uhhuh. Read error. Complain and punt. */
  66                 if (!buffer_uptodate(bh))
  67                         goto unlock;
  68 +               if (S_ISREG(inode->i_mode) &&
  69 +                   ext4_encrypted_inode(inode)) {
  70 +                       /* We expect the key to be set. */
  71 +                       BUG_ON(!ext4_has_encryption_key(inode));
  72 +                       BUG_ON(blocksize != PAGE_CACHE_SIZE);
  73 +                       WARN_ON_ONCE(ext4_decrypt_one(inode, page));
  74 +               }
  75         }
  76         if (ext4_should_journal_data(inode)) {
  77                 BUFFER_TRACE(bh, "get write access");
  78 diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
  79 index fff9fe6..171b9ac 100644
  80 --- a/fs/ext4/readpage.c
  81 +++ b/fs/ext4/readpage.c
  82 @@ -47,6 +47,46 @@
  83  #include "ext4.h"
  84
  85  /*
  86 + * Call ext4_decrypt on every single page, reusing the encryption
  87 + * context.
  88 + */
  89 +static void completion_pages(struct work_struct *work)
  90 +{
  91 +#ifdef CONFIG_EXT4_FS_ENCRYPTION
  92 +       struct ext4_crypto_ctx *ctx =
  93 +               container_of(work, struct ext4_crypto_ctx, work);
  94 +       struct bio      *bio    = ctx->bio;
  95 +       struct bio_vec  *bv;
  96 +       int             i;
  97 +
  98 +       bio_for_each_segment_all(bv, bio, i) {
  99 +               struct page *page = bv->bv_page;
 100 +
 101 +               int ret = ext4_decrypt(ctx, page);
 102 +               if (ret) {
 103 +                       WARN_ON_ONCE(1);
 104 +                       SetPageError(page);
 105 +               } else
 106 +                       SetPageUptodate(page);
 107 +               unlock_page(page);
 108 +       }
 109 +       ext4_release_crypto_ctx(ctx);
 110 +       bio_put(bio);
 111 +#else
 112 +       BUG();
 113 +#endif
 114 +}
 115 +
 116 +static inline bool ext4_bio_encrypted(struct bio *bio)
 117 +{
 118 +#ifdef CONFIG_EXT4_FS_ENCRYPTION
 119 +       return unlikely(bio->bi_private != NULL);
 120 +#else
 121 +       return false;
 122 +#endif
 123 +}
 124 +
 125 +/*
 126   * I/O completion handler for multipage BIOs.
 127   *
 128   * The mpage code never puts partial pages into a BIO (except for end-of-file).
 129 @@ -63,6 +103,18 @@ static void mpage_end_io(struct bio *bio, int err)
 130         struct bio_vec *bv;
 131         int i;
 132
 133 +       if (ext4_bio_encrypted(bio)) {
 134 +               struct ext4_crypto_ctx *ctx = bio->bi_private;
 135 +
 136 +               if (err) {
 137 +                       ext4_release_crypto_ctx(ctx);
 138 +               } else {
 139 +                       INIT_WORK(&ctx->work, completion_pages);
 140 +                       ctx->bio = bio;
 141 +                       queue_work(ext4_read_workqueue, &ctx->work);
 142 +                       return;
 143 +               }
 144 +       }
 145         bio_for_each_segment_all(bv, bio, i) {
 146                 struct page *page = bv->bv_page;
 147
 148 @@ -223,13 +275,25 @@ int ext4_mpage_readpages(struct address_space *mapping,
 149                         bio = NULL;
 150                 }
 151                 if (bio == NULL) {
 152 +                       struct ext4_crypto_ctx *ctx = NULL;
 153 +
 154 +                       if (ext4_encrypted_inode(inode) &&
 155 +                           S_ISREG(inode->i_mode)) {
 156 +                               ctx = ext4_get_crypto_ctx(inode);
 157 +                               if (IS_ERR(ctx))
 158 +                                       goto set_error_page;
 159 +                       }
 160                         bio = bio_alloc(GFP_KERNEL,
 161                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
 162 -                       if (!bio)
 163 +                       if (!bio) {
 164 +                               if (ctx)
 165 +                                       ext4_release_crypto_ctx(ctx);
 166                                 goto set_error_page;
 167 +                       }
 168                         bio->bi_bdev = bdev;
 169                         bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
 170                         bio->bi_end_io = mpage_end_io;
 171 +                       bio->bi_private = ctx;
 172                 }
 173
 174                 length = first_hole << blkbits;