Re: [PATCH 5/9] fscrypt: introduce fscrypt_prepare_readdir()

[Andreas Dilger <adilger@dilger.ca>]

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> On Nov 24, 2020, at 5:23 PM, Eric Biggers <ebiggers@kernel.org> wrote:
> 
> From: Eric Biggers <ebiggers@google.com>
> 
> The last remaining use of fscrypt_get_encryption_info() from filesystems
> is for readdir (->iterate_shared()).  Every other call is now in
> fs/crypto/ as part of some other higher-level operation.
> 
> We need to add a new argument to fscrypt_get_encryption_info() to
> indicate whether the encryption policy to allowed to be unrecognized or

(typo) *is* allowed

> not.  Doing this is easier if we can work with high-level operations
> rather than direct filesystem use of fscrypt_get_encryption_info().
> 
> So add a function fscrypt_prepare_readdir() which wraps the call to
> fscrypt_get_encryption_info() for the readdir use case.
> 
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> ---
> fs/crypto/hooks.c       |  6 ++++++
> fs/ext4/dir.c           |  8 +++-----
> fs/ext4/namei.c         |  2 +-
> fs/f2fs/dir.c           |  2 +-
> fs/ubifs/dir.c          |  2 +-
> include/linux/fscrypt.h | 24 ++++++++++++++++++++++++
> 6 files changed, 36 insertions(+), 8 deletions(-)
> 
> diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c
> index c809a4afa057..82f351d3113a 100644
> --- a/fs/crypto/hooks.c
> +++ b/fs/crypto/hooks.c
> @@ -114,6 +114,12 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
> }
> EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);
> 
> +int __fscrypt_prepare_readdir(struct inode *dir)
> +{
> +	return fscrypt_get_encryption_info(dir);
> +}
> +EXPORT_SYMBOL_GPL(__fscrypt_prepare_readdir);
> +
> /**
>  * fscrypt_prepare_setflags() - prepare to change flags with FS_IOC_SETFLAGS
>  * @inode: the inode on which flags are being changed
> diff --git a/fs/ext4/dir.c b/fs/ext4/dir.c
> index 16bfbdd5007c..c6d16353326a 100644
> --- a/fs/ext4/dir.c
> +++ b/fs/ext4/dir.c
> @@ -118,11 +118,9 @@ static int ext4_readdir(struct file *file, struct dir_context *ctx)
> 	struct buffer_head *bh = NULL;
> 	struct fscrypt_str fstr = FSTR_INIT(NULL, 0);
> 
> -	if (IS_ENCRYPTED(inode)) {
> -		err = fscrypt_get_encryption_info(inode);
> -		if (err)
> -			return err;
> -	}
> +	err = fscrypt_prepare_readdir(inode);
> +	if (err)
> +		return err;
> 
> 	if (is_dx_dir(inode)) {
> 		err = ext4_dx_readdir(file, ctx);
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 7b31aea3e025..5fa8436cd5fa 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -1004,7 +1004,7 @@ static int htree_dirblock_to_tree(struct file *dir_file,
> 					   EXT4_DIR_REC_LEN(0));
> 	/* Check if the directory is encrypted */
> 	if (IS_ENCRYPTED(dir)) {
> -		err = fscrypt_get_encryption_info(dir);
> +		err = fscrypt_prepare_readdir(dir);
> 		if (err < 0) {
> 			brelse(bh);
> 			return err;
> diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
> index 47bee953fc8d..049500f1e764 100644
> --- a/fs/f2fs/dir.c
> +++ b/fs/f2fs/dir.c
> @@ -1022,7 +1022,7 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
> 	int err = 0;
> 
> 	if (IS_ENCRYPTED(inode)) {
> -		err = fscrypt_get_encryption_info(inode);
> +		err = fscrypt_prepare_readdir(inode);
> 		if (err)
> 			goto out;
> 
> diff --git a/fs/ubifs/dir.c b/fs/ubifs/dir.c
> index 009fbf844d3e..1f33a5598b93 100644
> --- a/fs/ubifs/dir.c
> +++ b/fs/ubifs/dir.c
> @@ -514,7 +514,7 @@ static int ubifs_readdir(struct file *file, struct dir_context *ctx)
> 		return 0;
> 
> 	if (encrypted) {
> -		err = fscrypt_get_encryption_info(dir);
> +		err = fscrypt_prepare_readdir(dir);
> 		if (err)
> 			return err;
> 
> diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
> index 0c9e64969b73..8cbb26f55695 100644
> --- a/include/linux/fscrypt.h
> +++ b/include/linux/fscrypt.h
> @@ -242,6 +242,7 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
> 			     unsigned int flags);
> int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry,
> 			     struct fscrypt_name *fname);
> +int __fscrypt_prepare_readdir(struct inode *dir);
> int fscrypt_prepare_setflags(struct inode *inode,
> 			     unsigned int oldflags, unsigned int flags);
> int fscrypt_prepare_symlink(struct inode *dir, const char *target,
> @@ -537,6 +538,11 @@ static inline int __fscrypt_prepare_lookup(struct inode *dir,
> 	return -EOPNOTSUPP;
> }
> 
> +static inline int __fscrypt_prepare_readdir(struct inode *dir)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> static inline int fscrypt_prepare_setflags(struct inode *inode,
> 					   unsigned int oldflags,
> 					   unsigned int flags)
> @@ -795,6 +801,24 @@ static inline int fscrypt_prepare_lookup(struct inode *dir,
> 	return 0;
> }
> 
> +/**
> + * fscrypt_prepare_readdir() - prepare to read a possibly-encrypted directory
> + * @dir: the directory inode
> + *
> + * If the directory is encrypted and it doesn't already have its encryption key
> + * set up, try to set it up so that the filenames will be listed in plaintext
> + * form rather than in no-key form.
> + *
> + * Return: 0 on success; -errno on error.  Note that the encryption key being
> + *	   unavailable is not considered an error.
> + */
> +static inline int fscrypt_prepare_readdir(struct inode *dir)
> +{
> +	if (IS_ENCRYPTED(dir))
> +		return __fscrypt_prepare_readdir(dir);
> +	return 0;
> +}
> +
> /**
>  * fscrypt_prepare_setattr() - prepare to change a possibly-encrypted inode's
>  *			       attributes
> --
> 2.29.2
> 


Cheers, Andreas






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