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fscrypt: new helper function - fscrypt_prepare_lookup_partial()

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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: Luís Henriques <lhenriques@suse.de>
Tested-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Xiubo 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: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Luís Henriques 2023-03-16 18:14:11 +00:00 committed by Eric Biggers
parent 9c7fb7f763
commit 6f2656eab2
2 changed files with 37 additions and 0 deletions
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30
fs/crypto/hooks.c
View File

@ -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);

7
include/linux/fscrypt.h
View File

@ -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;