lock-inode-while-setting-encryption-policy

   1 fscrypto: lock inode while setting encryption policy
   2
   3 From: Eric Biggers <ebiggers@google.com>
   4
   5 i_rwsem needs to be acquired while setting an encryption policy so that
   6 concurrent calls to FS_IOC_SET_ENCRYPTION_POLICY are correctly
   7 serialized (especially the ->get_context() + ->set_context() pair), and
   8 so that new files cannot be created in the directory during or after the
   9 ->empty_dir() check.
  10
  11 Signed-off-by: Eric Biggers <ebiggers@google.com>
  12 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  13 Reviewed-by: Richard Weinberger <richard@nod.at>
  14 Cc: stable@vger.kernel.org
  15 ---
  16 Note: to be applied without conflict, this patch needs the changes from
  17 v4.8-rc6.
  18
  19 ---
  20  fs/crypto/policy.c | 4 ++++
  21  1 file changed, 4 insertions(+)
  22
  23 diff --git a/fs/crypto/policy.c b/fs/crypto/policy.c
  24 index ed115ac..6865663 100644
  25 --- a/fs/crypto/policy.c
  26 +++ b/fs/crypto/policy.c
  27 @@ -109,6 +109,8 @@ int fscrypt_process_policy(struct file *filp,
  28         if (ret)
  29                 return ret;
  30
  31 +       inode_lock(inode);
  32 +
  33         if (!inode_has_encryption_context(inode)) {
  34                 if (!S_ISDIR(inode->i_mode))
  35                         ret = -EINVAL;
  36 @@ -127,6 +129,8 @@ int fscrypt_process_policy(struct file *filp,
  37                 ret = -EINVAL;
  38         }
  39
  40 +       inode_unlock(inode);
  41 +
  42         mnt_drop_write_file(filp);
  43         return ret;
  44  }
  45 --
  46 2.8.0.rc3.226.g39d4020
  47
  48