Re: [PATCH v3] ceph: mark directory as non-complete complete after loading key

[Luís Henriques]

Xiubo Li <xiubli@xxxxxxxxxx> writes:

> On 22/11/2022 22:59, Luís Henriques wrote:
>> When setting a directory's crypt context, ceph_dir_clear_complete() needs to
>> be called otherwise if it was complete before, any existing (old) dentry will
>> still be valid.
>>
>> This patch adds a wrapper around __fscrypt_prepare_readdir() which will
>> ensure a directory is marked as non-complete if key status changes.
>>
>> Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
>> ---
>> Hi!
>>
>> Hopefully I'm not breaking anything else.  I've run a bunch of fstests and
>> didn't saw any (new) failures.
>>
>> Changes since v2:
>> - Created helper wrapper for __fscrypt_prepare_readdir()
>> - Added calls to the new helper
>>
>> Changes since v1:
>> - Moved the __ceph_dir_clear_complete() call from ceph_crypt_get_context()
>>    to ceph_lookup().
>> - Added an __fscrypt_prepare_readdir() wrapper to check key status changes
>>
>>   fs/ceph/crypto.c     | 35 +++++++++++++++++++++++++++++++++--
>>   fs/ceph/crypto.h     |  6 ++++++
>>   fs/ceph/dir.c        |  8 ++++----
>>   fs/ceph/mds_client.c |  6 +++---
>>   4 files changed, 46 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
>> index 35a2ccfe6899..5ef65a06af98 100644
>> --- a/fs/ceph/crypto.c
>> +++ b/fs/ceph/crypto.c
>> @@ -397,8 +397,8 @@ int ceph_fname_to_usr(const struct ceph_fname *fname, struct fscrypt_str *tname,
>>   		goto out_inode;
>>   	}
>>   -	ret = __fscrypt_prepare_readdir(dir);
>> -	if (ret)
>> +	ret = ceph_fscrypt_prepare_readdir(dir);
>> +	if (ret < 0)
>>   		goto out_inode;
>>     	/*
>> @@ -636,3 +636,34 @@ int ceph_fscrypt_encrypt_pages(struct inode *inode, struct page **page, u64 off,
>>   	}
>>   	return ret;
>>   }
>> +
>> +/**
>> + * ceph_fscrypt_prepare_readdir - simple __fscrypt_prepare_readdir() wrapper
>> + * @dir: directory inode for readdir prep
>> + *
>> + * Simple wrapper around __fscrypt_prepare_readdir() that will mark directory as
>> + * non-complete if this call results in having the directory unlocked.
>> + *
>> + * Returns:
>> + *     1 - if directory was locked and key is now loaded (i.e. dir is unlocked)
>> + *     0 - if directory is still locked
>> + *   < 0 - if __fscrypt_prepare_readdir() fails
>> + */
>> +int ceph_fscrypt_prepare_readdir(struct inode *dir)
>> +{
>> +	bool had_key = fscrypt_has_encryption_key(dir);
>> +	int err;
>> +
>> +	if (!IS_ENCRYPTED(dir))
>> +		return 0;
>> +
>> +	err = __fscrypt_prepare_readdir(dir);
>> +	if (err)
>> +		return err;
>> +	if (!had_key && fscrypt_has_encryption_key(dir)) {
>> +		/* directory just got unlocked, mark it as not complete */
>> +		ceph_dir_clear_complete(dir);
>> +		return 1;
>> +	}
>> +	return 0;
>> +}
>> diff --git a/fs/ceph/crypto.h b/fs/ceph/crypto.h
>> index c6ee993f4ec8..cad53ec916fd 100644
>> --- a/fs/ceph/crypto.h
>> +++ b/fs/ceph/crypto.h
>> @@ -154,6 +154,7 @@ int ceph_fscrypt_decrypt_extents(struct inode *inode, struct page **page, u64 of
>>   				 struct ceph_sparse_extent *map, u32 ext_cnt);
>>   int ceph_fscrypt_encrypt_pages(struct inode *inode, struct page **page, u64 off,
>>   				int len, gfp_t gfp);
>> +int ceph_fscrypt_prepare_readdir(struct inode *dir);
>>     static inline struct page *ceph_fscrypt_pagecache_page(struct page *page)
>>   {
>> @@ -254,6 +255,11 @@ static inline struct page *ceph_fscrypt_pagecache_page(struct page *page)
>>   {
>>   	return page;
>>   }
>> +
>> +static inline int ceph_fscrypt_prepare_readdir(struct inode *dir)
>> +{
>> +	return 0;
>> +}
>>   #endif /* CONFIG_FS_ENCRYPTION */
>>     static inline loff_t ceph_fscrypt_page_offset(struct page *page)
>> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
>> index edc2bf0aab83..5829f27d058d 100644
>> --- a/fs/ceph/dir.c
>> +++ b/fs/ceph/dir.c
>> @@ -343,8 +343,8 @@ static int ceph_readdir(struct file *file, struct dir_context *ctx)
>>   		ctx->pos = 2;
>>   	}
>>   -	err = fscrypt_prepare_readdir(inode);
>> -	if (err)
>> +	err = ceph_fscrypt_prepare_readdir(inode);
>> +	if (err < 0)
>>   		return err;
>>     	spin_lock(&ci->i_ceph_lock);
>> @@ -784,8 +784,8 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
>>   		return ERR_PTR(-ENAMETOOLONG);
>>     	if (IS_ENCRYPTED(dir)) {
>> -		err = __fscrypt_prepare_readdir(dir);
>> -		if (err)
>> +		err = ceph_fscrypt_prepare_readdir(dir);
>> +		if (err < 0)
>>   			return ERR_PTR(err);
>>   		if (!fscrypt_has_encryption_key(dir)) {
>>   			spin_lock(&dentry->d_lock);
>> diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
>> index 9518ac8e407d..4becc9eada4b 100644
>> --- a/fs/ceph/mds_client.c
>> +++ b/fs/ceph/mds_client.c
>> @@ -2551,8 +2551,8 @@ static u8 *get_fscrypt_altname(const struct ceph_mds_request *req, u32 *plen)
>>   	if (!IS_ENCRYPTED(dir))
>>   		goto success;
>>   -	ret = __fscrypt_prepare_readdir(dir);
>> -	if (ret)
>> +	ret = ceph_fscrypt_prepare_readdir(dir);
>> +	if (ret < 0)
>>   		return ERR_PTR(ret);
>>     	/* No key? Just ignore it. */
>> @@ -2668,7 +2668,7 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase, int for
>>   			spin_unlock(&cur->d_lock);
>>   			parent = dget_parent(cur);
>>   -			ret = __fscrypt_prepare_readdir(d_inode(parent));
>> +			ret = ceph_fscrypt_prepare_readdir(d_inode(parent));
>>   			if (ret < 0) {
>>   				dput(parent);
>>   				dput(cur);
>
> Hi Luis,
>
> This version LGTM.
>
> Just one nit. I think the following:
>
> if (fscrypt_has_encryption_key(d_inode(parent))) {
>
> is no needed any more.
>
> We can just switch to:
>
> if (ret) {
>
> And also other places ?

No, that won't work, and I found that out the hard way :-)

If the directory is unlocked (i.e. the key is loaded), then the helper
function ceph_fscrypt_prepare_readdir() will return '0' because the status
hasn't change.  Thus, we still need to check that here.

Cheers,
-- 
Luís