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 Change-Id: Ie9c043a132a01da60d1617662cd30307639f5599
   6 Signed-off-by: Michael Halcrow <mhalcrow@google.com>
   7 Signed-off-by: Ildar Muslukhov <ildarm@google.com>
   8 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
   9 ---
  10  fs/ext4/file.c     | 19 +++++++++++++++++--
  11  fs/ext4/inode.c    |  8 ++++++++
  12  fs/ext4/readpage.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
  13  3 files changed, 90 insertions(+), 3 deletions(-)
  14
  15 diff --git a/fs/ext4/file.c b/fs/ext4/file.c
  16 index 8131be8..756d10f 100644
  17 --- a/fs/ext4/file.c
  18 +++ b/fs/ext4/file.c
  19 @@ -28,6 +28,7 @@
  20  #include <linux/pagevec.h>
  21  #include "ext4.h"
  22  #include "ext4_jbd2.h"
  23 +#include "ext4_crypto.h"
  24  #include "xattr.h"
  25  #include "acl.h"
  26
  27 @@ -200,6 +201,13 @@ static const struct vm_operations_struct ext4_file_vm_ops = {
  28
  29  static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
  30  {
  31 +       struct inode *inode = file->f_mapping->host;
  32 +
  33 +       if (ext4_encrypted_inode(inode)) {
  34 +               int err = ext4_generate_encryption_key(inode);
  35 +               if (err)
  36 +                       return 0;
  37 +       }
  38         file_accessed(file);
  39         vma->vm_ops = &ext4_file_vm_ops;
  40         return 0;
  41 @@ -212,6 +220,7 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
  42         struct vfsmount *mnt = filp->f_path.mnt;
  43         struct path path;
  44         char buf[64], *cp;
  45 +       int ret;
  46
  47         if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
  48                      !(sb->s_flags & MS_RDONLY))) {
  49 @@ -250,11 +259,17 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
  50          * writing and the journal is present
  51          */
  52         if (filp->f_mode & FMODE_WRITE) {
  53 -               int ret = ext4_inode_attach_jinode(inode);
  54 +               ret = ext4_inode_attach_jinode(inode);
  55                 if (ret < 0)
  56                         return ret;
  57         }
  58 -       return dquot_file_open(inode, filp);
  59 +       ret = dquot_file_open(inode, filp);
  60 +       if (!ret && ext4_encrypted_inode(inode)) {
  61 +               ret = ext4_generate_encryption_key(inode);
  62 +               if (ret)
  63 +                       ret = -EACCES;
  64 +       }
  65 +       return ret;
  66  }
  67
  68  /*
  69 diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
  70 index dcc836c..5b6b7b6 100644
  71 --- a/fs/ext4/inode.c
  72 +++ b/fs/ext4/inode.c
  73 @@ -39,6 +39,7 @@
  74  #include <linux/ratelimit.h>
  75  #include <linux/aio.h>
  76  #include <linux/bitops.h>
  77 +#include <linux/prefetch.h>
  78
  79  #include "ext4_jbd2.h"
  80  #include "ext4_crypto.h"
  81 @@ -3363,6 +3364,13 @@ static int ext4_block_zero_page_range(handle_t *handle,
  82                 /* Uhhuh. Read error. Complain and punt. */
  83                 if (!buffer_uptodate(bh))
  84                         goto unlock;
  85 +               if (S_ISREG(inode->i_mode) &&
  86 +                   ext4_encrypted_inode(inode)) {
  87 +                       /* We expect the key to be set. */
  88 +                       BUG_ON(!ext4_has_encryption_key(inode));
  89 +                       BUG_ON(blocksize != PAGE_CACHE_SIZE);
  90 +                       WARN_ON_ONCE(ext4_decrypt_one(inode, page));
  91 +               }
  92         }
  93         if (ext4_should_journal_data(inode)) {
  94                 BUFFER_TRACE(bh, "get write access");
  95 diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
  96 index fff9fe6..171b9ac 100644
  97 --- a/fs/ext4/readpage.c
  98 +++ b/fs/ext4/readpage.c
  99 @@ -47,6 +47,46 @@
 100  #include "ext4.h"
 101
 102  /*
 103 + * Call ext4_decrypt on every single page, reusing the encryption
 104 + * context.
 105 + */
 106 +static void completion_pages(struct work_struct *work)
 107 +{
 108 +#ifdef CONFIG_EXT4_FS_ENCRYPTION
 109 +       struct ext4_crypto_ctx *ctx =
 110 +               container_of(work, struct ext4_crypto_ctx, work);
 111 +       struct bio      *bio    = ctx->bio;
 112 +       struct bio_vec  *bv;
 113 +       int             i;
 114 +
 115 +       bio_for_each_segment_all(bv, bio, i) {
 116 +               struct page *page = bv->bv_page;
 117 +
 118 +               int ret = ext4_decrypt(ctx, page);
 119 +               if (ret) {
 120 +                       WARN_ON_ONCE(1);
 121 +                       SetPageError(page);
 122 +               } else
 123 +                       SetPageUptodate(page);
 124 +               unlock_page(page);
 125 +       }
 126 +       ext4_release_crypto_ctx(ctx);
 127 +       bio_put(bio);
 128 +#else
 129 +       BUG();
 130 +#endif
 131 +}
 132 +
 133 +static inline bool ext4_bio_encrypted(struct bio *bio)
 134 +{
 135 +#ifdef CONFIG_EXT4_FS_ENCRYPTION
 136 +       return unlikely(bio->bi_private != NULL);
 137 +#else
 138 +       return false;
 139 +#endif
 140 +}
 141 +
 142 +/*
 143   * I/O completion handler for multipage BIOs.
 144   *
 145   * The mpage code never puts partial pages into a BIO (except for end-of-file).
 146 @@ -63,6 +103,18 @@ static void mpage_end_io(struct bio *bio, int err)
 147         struct bio_vec *bv;
 148         int i;
 149
 150 +       if (ext4_bio_encrypted(bio)) {
 151 +               struct ext4_crypto_ctx *ctx = bio->bi_private;
 152 +
 153 +               if (err) {
 154 +                       ext4_release_crypto_ctx(ctx);
 155 +               } else {
 156 +                       INIT_WORK(&ctx->work, completion_pages);
 157 +                       ctx->bio = bio;
 158 +                       queue_work(ext4_read_workqueue, &ctx->work);
 159 +                       return;
 160 +               }
 161 +       }
 162         bio_for_each_segment_all(bv, bio, i) {
 163                 struct page *page = bv->bv_page;
 164
 165 @@ -223,13 +275,25 @@ int ext4_mpage_readpages(struct address_space *mapping,
 166                         bio = NULL;
 167                 }
 168                 if (bio == NULL) {
 169 +                       struct ext4_crypto_ctx *ctx = NULL;
 170 +
 171 +                       if (ext4_encrypted_inode(inode) &&
 172 +                           S_ISREG(inode->i_mode)) {
 173 +                               ctx = ext4_get_crypto_ctx(inode);
 174 +                               if (IS_ERR(ctx))
 175 +                                       goto set_error_page;
 176 +                       }
 177                         bio = bio_alloc(GFP_KERNEL,
 178                                 min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
 179 -                       if (!bio)
 180 +                       if (!bio) {
 181 +                               if (ctx)
 182 +                                       ext4_release_crypto_ctx(ctx);
 183                                 goto set_error_page;
 184 +                       }
 185                         bio->bi_bdev = bdev;
 186                         bio->bi_iter.bi_sector = blocks[0] << (blkbits - 9);
 187                         bio->bi_end_io = mpage_end_io;
 188 +                       bio->bi_private = ctx;
 189                 }
 190
 191                 length = first_hole << blkbits;