diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 069088e91ea9..8b90217320dd 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -47,3 +47,18 @@ int fscrypt_file_open(struct inode *inode, struct file *filp) return err; } EXPORT_SYMBOL_GPL(fscrypt_file_open); + +int __fscrypt_prepare_link(struct inode *inode, struct inode *dir) +{ + int err; + + err = fscrypt_require_key(dir); + if (err) + return err; + + if (!fscrypt_has_permitted_context(dir, inode)) + return -EPERM; + + return 0; +} +EXPORT_SYMBOL_GPL(__fscrypt_prepare_link); diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h index cc86d49c820d..6ceb76abd842 100644 --- a/include/linux/fscrypt.h +++ b/include/linux/fscrypt.h @@ -178,4 +178,31 @@ static inline int fscrypt_require_key(struct inode *inode) return 0; } +/** + * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory + * @old_dentry: an existing dentry for the inode being linked + * @dir: the target directory + * @dentry: negative dentry for the target filename + * + * A new link can only be added to an encrypted directory if the directory's + * encryption key is available --- since otherwise we'd have no way to encrypt + * the filename. Therefore, we first set up the directory's encryption key (if + * not already done) and return an error if it's unavailable. + * + * We also verify that the link will not violate the constraint that all files + * in an encrypted directory tree use the same encryption policy. + * + * Return: 0 on success, -ENOKEY if the directory's encryption key is missing, + * -EPERM if the link would result in an inconsistent encryption policy, or + * another -errno code. + */ +static inline int fscrypt_prepare_link(struct dentry *old_dentry, + struct inode *dir, + struct dentry *dentry) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_link(d_inode(old_dentry), dir); + return 0; +} + #endif /* _LINUX_FSCRYPT_H */ diff --git a/include/linux/fscrypt_notsupp.h b/include/linux/fscrypt_notsupp.h index ea26d4c609df..a80917bc2102 100644 --- a/include/linux/fscrypt_notsupp.h +++ b/include/linux/fscrypt_notsupp.h @@ -187,4 +187,10 @@ static inline int fscrypt_file_open(struct inode *inode, struct file *filp) return 0; } +static inline int __fscrypt_prepare_link(struct inode *inode, + struct inode *dir) +{ + return -EOPNOTSUPP; +} + #endif /* _LINUX_FSCRYPT_NOTSUPP_H */ diff --git a/include/linux/fscrypt_supp.h b/include/linux/fscrypt_supp.h index 0551352156e4..547cdbd04f17 100644 --- a/include/linux/fscrypt_supp.h +++ b/include/linux/fscrypt_supp.h @@ -146,5 +146,6 @@ extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t, /* hooks.c */ extern int fscrypt_file_open(struct inode *inode, struct file *filp); +extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir); #endif /* _LINUX_FSCRYPT_SUPP_H */