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fscrypt: new helper function - fscrypt_prepare_lookup()

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Introduce a helper function which prepares to look up the given dentry
in the given directory.  If the directory is encrypted, it handles
loading the directory's encryption key, setting the dentry's ->d_op to
fscrypt_d_ops, and setting DCACHE_ENCRYPTED_WITH_KEY if the directory's
encryption key is available.

Note: once all filesystems switch over to this, we'll be able to move
fscrypt_d_ops and fscrypt_set_encrypted_dentry() to fscrypt_private.h.

Acked-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Eric Biggers 2017-10-09 12:15:43 -07:00 committed by Theodore Ts'o
parent 94b26f3672
commit 32c3cf028e
4 changed files with 53 additions and 0 deletions
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18
fs/crypto/hooks.c
View file

@ -92,3 +92,21 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry,
return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename);
int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry)
{
int err = fscrypt_get_encryption_info(dir);
if (err)
return err;
if (fscrypt_has_encryption_key(dir)) {
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
spin_unlock(&dentry->d_lock);
}
d_set_d_op(dentry, &fscrypt_d_ops);
return 0;
}
EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup);

28
include/linux/fscrypt.h
View file

@ -237,4 +237,32 @@ static inline int fscrypt_prepare_rename(struct inode *old_dir,
return 0;
}
/**
* fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory
* @dir: directory being searched
* @dentry: filename being looked up
* @flags: lookup flags
*
* Prepare for ->lookup() in a directory which may be encrypted. Lookups can be
* done with or without the directory's encryption key; without the key,
* filenames are presented in encrypted form. Therefore, we'll try to set up
* the directory's encryption key, but even without it the lookup can continue.
*
* To allow invalidating stale dentries if the directory's encryption key is
* added later, we also install a custom ->d_revalidate() method and use the
* DCACHE_ENCRYPTED_WITH_KEY flag to indicate whether a given dentry is a
* plaintext name (flag set) or a ciphertext name (flag cleared).
*
* Return: 0 on success, -errno if a problem occurred while setting up the
* encryption key
*/
static inline int fscrypt_prepare_lookup(struct inode *dir,
struct dentry *dentry,
unsigned int flags)
{
if (IS_ENCRYPTED(dir))
return __fscrypt_prepare_lookup(dir, dentry);
return 0;
}
#endif /* _LINUX_FSCRYPT_H */

6
include/linux/fscrypt_notsupp.h
View file

@ -201,4 +201,10 @@ static inline int __fscrypt_prepare_rename(struct inode *old_dir,
return -EOPNOTSUPP;
}
static inline int __fscrypt_prepare_lookup(struct inode *dir,
struct dentry *dentry)
{
return -EOPNOTSUPP;
}
#endif /* _LINUX_FSCRYPT_NOTSUPP_H */

1
include/linux/fscrypt_supp.h
View file

@ -151,5 +151,6 @@ extern int __fscrypt_prepare_rename(struct inode *old_dir,
struct inode *new_dir,
struct dentry *new_dentry,
unsigned int flags);
extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
#endif /* _LINUX_FSCRYPT_SUPP_H */