crypto-fix-validate-when-key-add-remove

   1 ext4 crypto: revalidate dentry after adding or removing the key
   2
   3 Add a validation check for dentries for encrypted directory to make
   4 sure we're not caching stale data after a key has been added or removed.
   5
   6 Also check to make sure that status of the encryption key is updated
   7 when readdir(2) is executed.
   8
   9 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  10
  11 ---
  12  fs/ext4/crypto.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
  13  fs/ext4/dir.c    |  6 ++++++
  14  fs/ext4/ext4.h   |  1 +
  15  fs/ext4/namei.c  | 18 ++++++++++++++++++
  16  4 files changed, 81 insertions(+)
  17
  18 diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
  19 index c802120..38f7562 100644
  20 --- a/fs/ext4/crypto.c
  21 +++ b/fs/ext4/crypto.c
  22 @@ -467,3 +467,59 @@ uint32_t ext4_validate_encryption_key_size(uint32_t mode, uint32_t size)
  23                 return size;
  24         return 0;
  25  }
  26 +
  27 +/*
  28 + * Validate dentries for encrypted directories to make sure we aren't
  29 + * potentially caching stale data after a key has been added or
  30 + * removed.
  31 + */
  32 +static int ext4_d_revalidate(struct dentry *dentry, unsigned int flags)
  33 +{
  34 +       struct inode *dir = d_inode(dentry->d_parent);
  35 +       struct ext4_crypt_info *ci = EXT4_I(dir)->i_crypt_info;
  36 +       int dir_has_key, cached_with_key;
  37 +
  38 +       if (!ext4_encrypted_inode(dir))
  39 +               return 0;
  40 +
  41 +       if (ci && ci->ci_keyring_key &&
  42 +           (ci->ci_keyring_key->flags & ((1 << KEY_FLAG_INVALIDATED) |
  43 +                                         (1 << KEY_FLAG_REVOKED) |
  44 +                                         (1 << KEY_FLAG_DEAD))))
  45 +               ci = NULL;
  46 +
  47 +       /* this should eventually be an flag in d_flags */
  48 +       cached_with_key = dentry->d_fsdata != NULL;
  49 +       dir_has_key = (ci != NULL);
  50 +
  51 +       /*
  52 +        * If the dentry was cached without the key, and it is a
  53 +        * negative dentry, it might be a valid name.  We can't check
  54 +        * if the key has since been made available due to locking
  55 +        * reasons, so we fail the validation so ext4_lookup() can do
  56 +        * this check.
  57 +        *
  58 +        * We also fail the validation if the dentry was created with
  59 +        * the key present, but we no longer have the key, or vice versa.
  60 +        */
  61 +       if ((!cached_with_key && d_is_negative(dentry)) ||
  62 +           (!cached_with_key && dir_has_key) ||
  63 +           (cached_with_key && !dir_has_key)) {
  64 +#if 0                          /* Revalidation debug */
  65 +               char buf[80];
  66 +               char *cp = simple_dname(dentry, buf, sizeof(buf));
  67 +
  68 +               if (IS_ERR(cp))
  69 +                       cp = (char *) "???";
  70 +               pr_err("revalidate: %s %p %d %d %d\n", cp, dentry->d_fsdata,
  71 +                      cached_with_key, d_is_negative(dentry),
  72 +                      dir_has_key);
  73 +#endif
  74 +               return 0;
  75 +       }
  76 +       return 1;
  77 +}
  78 +
  79 +const struct dentry_operations ext4_encrypted_d_ops = {
  80 +       .d_revalidate = ext4_d_revalidate,
  81 +};
  82 diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
  83 index 1d1bca7..6d17f31 100644
  84 --- a/fs/ext4/dir.c
  85 +++ b/fs/ext4/dir.c
  86 @@ -111,6 +111,12 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
  87         int dir_has_error = 0;
  88         struct ext4_str fname_crypto_str = {.name = NULL, .len = 0};
  89
  90 +       if (ext4_encrypted_inode(inode)) {
  91 +               err = ext4_get_encryption_info(inode);
  92 +               if (err && err != -ENOKEY)
  93 +                       return err;
  94 +       }
  95 +
  96         if (is_dx_dir(inode)) {
  97                 err = ext4_dx_readdir(file, ctx);
  98                 if (err != ERR_BAD_DX_DIR) {
  99 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
 100 index 0662b28..157b458a 100644
 101 --- a/fs/ext4/ext4.h
 102 +++ b/fs/ext4/ext4.h
 103 @@ -2302,6 +2302,7 @@ struct page *ext4_encrypt(struct inode *inode,
 104  int ext4_decrypt(struct page *page);
 105  int ext4_encrypted_zeroout(struct inode *inode, ext4_lblk_t lblk,
 106                            ext4_fsblk_t pblk, ext4_lblk_t len);
 107 +extern const struct dentry_operations ext4_encrypted_d_ops;
 108
 109  #ifdef CONFIG_EXT4_FS_ENCRYPTION
 110  int ext4_init_crypto(void);
 111 diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
 112 index 06574dd..5de8483 100644
 113 --- a/fs/ext4/namei.c
 114 +++ b/fs/ext4/namei.c
 115 @@ -1558,6 +1558,24 @@ static struct dentry *ext4_lookup(struct inode *dir, struct dentry *dentry, unsi
 116         struct ext4_dir_entry_2 *de;
 117         struct buffer_head *bh;
 118
 119 +       if (ext4_encrypted_inode(dir)) {
 120 +               int res = ext4_get_encryption_info(dir);
 121 +
 122 +               /*
 123 +                * This should be a properly defined flag for
 124 +                * dentry->d_flags when we uplift this to the VFS.
 125 +                * d_fsdata is set to (void *) 1 if if the dentry is
 126 +                * created while the directory was encrypted and we
 127 +                * don't have access to the key.
 128 +                */
 129 +              dentry->d_fsdata = NULL;
 130 +              if (ext4_encryption_info(dir))
 131 +                      dentry->d_fsdata = (void *) 1;
 132 +              d_set_d_op(dentry, &ext4_encrypted_d_ops);
 133 +              if (res && res != -ENOKEY)
 134 +                      return ERR_PTR(res);
 135 +       }
 136 +
 137         if (dentry->d_name.len > EXT4_NAME_LEN)
 138                 return ERR_PTR(-ENAMETOOLONG);
 139