Commit 6f2656ea authored by Luís Henriques's avatar Luís Henriques Committed by Eric Biggers
Browse files

fscrypt: new helper function - fscrypt_prepare_lookup_partial() 



This patch introduces a new helper function which can be used both in
lookups and in atomic_open operations by filesystems that want to handle
filename encryption and no-key dentries themselves.

The reason for this function to be used in atomic open is that this
operation can act as a lookup if handed a dentry that is negative.  And in
this case we may need to set DCACHE_NOKEY_NAME.

Signed-off-by: default avatarLuís Henriques <lhenriques@suse.de>
Tested-by: default avatarXiubo Li <xiubli@redhat.com>
Reviewed-by: default avatarXiubo Li <xiubli@redhat.com>
[ebiggers: improved the function comment, and moved the function to just
           below __fscrypt_prepare_lookup()]
Link: https://lore.kernel.org/r/20230320220149.21863-1-ebiggers@kernel.org


Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
parent 9c7fb7f7

fs/crypto/hooks.c

+30 −0
Original line number Diff line number Diff line
@@ -111,6 +111,36 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, 
}

EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);



/**

 * fscrypt_prepare_lookup_partial() - prepare lookup without filename setup

 * @dir: the encrypted directory being searched

 * @dentry: the dentry being looked up in @dir

 *

 * This function should be used by the ->lookup and ->atomic_open methods of

 * filesystems that handle filename encryption and no-key name encoding

 * themselves and thus can't use fscrypt_prepare_lookup().  Like

 * fscrypt_prepare_lookup(), this will try to set up the directory's encryption

 * key and will set DCACHE_NOKEY_NAME on the dentry if the key is unavailable.

 * However, this function doesn't set up a struct fscrypt_name for the filename.

 *

 * Return: 0 on success; -errno on error.  Note that the encryption key being

 *	   unavailable is not considered an error.  It is also not an error if

 *	   the encryption policy is unsupported by this kernel; that is treated

 *	   like the key being unavailable, so that files can still be deleted.

 */

int fscrypt_prepare_lookup_partial(struct inode *dir, struct dentry *dentry)

{

	int err = fscrypt_get_encryption_info(dir, true);



	if (!err && !fscrypt_has_encryption_key(dir)) {

		spin_lock(&dentry->d_lock);

		dentry->d_flags |= DCACHE_NOKEY_NAME;

		spin_unlock(&dentry->d_lock);

	}

	return err;

}

EXPORT_SYMBOL_GPL(fscrypt_prepare_lookup_partial);



int __fscrypt_prepare_readdir(struct inode *dir)

{

	return fscrypt_get_encryption_info(dir, true);

include/linux/fscrypt.h

+7 −0
Original line number Diff line number Diff line
@@ -359,6 +359,7 @@ 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_lookup_partial(struct inode *dir, struct dentry *dentry);

int __fscrypt_prepare_readdir(struct inode *dir);

int __fscrypt_prepare_setattr(struct dentry *dentry, struct iattr *attr);

int fscrypt_prepare_setflags(struct inode *inode,
@@ -673,6 +674,12 @@ static inline int __fscrypt_prepare_lookup(struct inode *dir, 
	return -EOPNOTSUPP;

}



static inline int fscrypt_prepare_lookup_partial(struct inode *dir,

						 struct dentry *dentry)

{

	return -EOPNOTSUPP;

}



static inline int __fscrypt_prepare_readdir(struct inode *dir)

{

	return -EOPNOTSUPP;