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Commit 249c9041 authored by Eric Biggers's avatar Eric Biggers Committed by Jaegeuk Kim
Browse files

fscrypt: new helper function - fscrypt_prepare_setattr() 



Introduce a helper function for filesystems to call when processing
->setattr() on a possibly-encrypted inode.  It handles enforcing that an
encrypted file can only be truncated if its encryption key is available.

Acked-by: default avatarDave Chinner <dchinner@redhat.com>
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent 91d09c05

include/linux/fscrypt.h

+25 −0
Original line number Diff line number Diff line
@@ -266,4 +266,29 @@ static inline int fscrypt_prepare_lookup(struct inode *dir, 
	return 0;

}



/**

 * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes

 * @dentry: dentry through which the inode is being changed

 * @attr: attributes to change

 *

 * Prepare for ->setattr() on a possibly-encrypted inode.  On an encrypted file,

 * most attribute changes are allowed even without the encryption key.  However,

 * without the encryption key we do have to forbid truncates.  This is needed

 * because the size being truncated to may not be a multiple of the filesystem

 * block size, and in that case we'd have to decrypt the final block, zero the

 * portion past i_size, and re-encrypt it.  (We *could* allow truncating to a

 * filesystem block boundary, but it's simpler to just forbid all truncates ---

 * and we already forbid all other contents modifications without the key.)

 *

 * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code

 * if a problem occurred while setting up the encryption key.

 */

static inline int fscrypt_prepare_setattr(struct dentry *dentry,

					  struct iattr *attr)

{

	if (attr->ia_valid & ATTR_SIZE)

		return fscrypt_require_key(d_inode(dentry));

	return 0;

}



#endif	/* _LINUX_FSCRYPT_H */