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Subject: Re: [PATCH] ceph: make sure directories aren't complete after setting
 crypt context
To:     =?UTF-8?Q?Lu=c3=ads_Henriques?= <lhenriques@suse.de>
Cc:     Ilya Dryomov <idryomov@gmail.com>,
        Jeff Layton <jlayton@kernel.org>, ceph-devel@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20221116153703.27292-1-lhenriques@suse.de>
 <5de0ae69-5e3d-2ccb-64a3-971db66477f8@redhat.com>
 <41710b3d-b37f-8c65-d55d-c4137a366efd@redhat.com> <87o7t5mpby.fsf@suse.de>
 <116d12db-5c24-9a57-79a9-b7a02a0bb4c2@redhat.com> <87k03sms8b.fsf@suse.de>
From:   Xiubo Li <xiubli@redhat.com>
Message-ID: <f8067bfb-95d6-c24a-8f2e-aa2229a74924@redhat.com>
Date:   Mon, 21 Nov 2022 08:53:49 +0800
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On 18/11/2022 19:12, Luís Henriques wrote:
> Xiubo Li <xiubli@redhat.com> writes:
>
>> On 18/11/2022 02:02, Luís Henriques wrote:
>>> Xiubo Li <xiubli@redhat.com> writes:
>>>
>>>> On 17/11/2022 16:03, Xiubo Li wrote:
>>>>> On 16/11/2022 23:37, Luís Henriques wrote:
>>>>>> When setting a directory's crypt context, __ceph_dir_clear_complete() needs
>>>>>> to be used otherwise, if it was complete before, any old dentry that's still
>>>>>> around will be valid.
>>>>>>
>>>>>> Signed-off-by: Luís Henriques <lhenriques@suse.de>
>>>>>> ---
>>>>>> Hi!
>>>>>>
>>>>>> Here's a simple way to trigger the bug this patch is fixing:
>>>>>>
>>>>>> # cd /cephfs
>>>>>> # ls mydir
>>>>>> nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0
>>>>>> # ls mydir/nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0/
>>>>>> Cyuer5xT+kBlEPgtwAqSj0WK2taEljP5vHZ,D8VXCJ8
>>>>>> u+46b2XVCt7Obpz0gznZyNLRj79Q2l4KmkwbKOzdQKw
>>>>>> # fscrypt unlock mydir
>>>>>> # touch /mnt/test/mydir/mysubdir/file
>>>>>> touch: cannot touch '/mnt/test/mydir/mysubdir/file': No such file or
>>>>>> directory
>>>>>>
>>>>>>     fs/ceph/crypto.c | 4 ++++
>>>>>>     1 file changed, 4 insertions(+)
>>>>>>
>>>>>> diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
>>>>>> index 35a2ccfe6899..dc1557967032 100644
>>>>>> --- a/fs/ceph/crypto.c
>>>>>> +++ b/fs/ceph/crypto.c
>>>>>> @@ -87,6 +87,10 @@ static int ceph_crypt_get_context(struct inode *inode,
>>>>>> void *ctx, size_t len)
>>>>>>             return -ERANGE;
>>>>>>           memcpy(ctx, cfa->cfa_blob, ctxlen);
>>>>>> +
>>>>>> +    /* Directory isn't complete anymore */
>>>>>> +    if (S_ISDIR(inode->i_mode) && __ceph_dir_is_complete(ci))
>>>>>> +        __ceph_dir_clear_complete(ci);
>>>>> Hi Luis,
>>>>>
>>>>> Good catch!
>>>>>
>>>>> BTW, why do this in the ceph_crypt_get_context() ? As my understanding is that
>>>>> we should mark 'mydir' as incomplete when unlocking it. While as I remembered
>>>>> the unlock operation will do:
>>>>>
>>>>>
>>>>> Step1: get_encpolicy via 'mydir' as ctx
>>>>> Step2: rm_enckey of ctx from the superblock
>>>>>
>>>> Sorry, it should be add_enckey.
>>>>> Since I am still running the test cases for the file lock patches, so I didn't
>>>>> catch logs to confirm the above steps yet.
>>>>>
>>>>> If I am right IMO then we should mark the dir as incomplete in the Step2
>>>>> instead, because for non-unlock operations they may also do the Step1.
>>>>>
>>>> Your patch will work. But probably we should do this just around
>>>> __fscrypt_prepare_readdir() or fscrypt_prepare_readdir() instead ? We need to
>>>> detect that once the 'inode->i_crypt_info' changed then mark the dir as
>>>> incomplete.
>>>>
>>>> For now for the lock operation it will evict the inode, which will help do this
>>>> for us already. But for unlock case, we need to handle it by ourself.
>>> OK, that makes sense and to be honest I thought that there should be
>>> another place for doing this. Unfortunately, I didn't found it: in the
>>> test case I have the fscrypt_prepare_readdir() isn't called:
>>>
>>>      # cd /cephfs
>>>      # ls mydir
>>>      nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0
>>>      # ls mydir/nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0/
>>>      Cyuer5xT+kBlEPgtwAqSj0WK2taEljP5vHZ,D8VXCJ8 u+46b2XVCt7Obpz0gznZyNLRj79Q2l4KmkwbKOzdQKw
>>>
>>> At this point readdir was executed, of course.  And
>>> __ceph_dir_set_complete() is also used to indicate that we have the full
>>> contents.  However, executing the following commands won't result in any
>>> new readdir():
>>>
>>>      # fscrypt unlock mydir
>>>      # touch /mnt/test/mydir/mysubdir/file
>>>
>>> and since the encryption key is set at the sb level, I couldn't find a way
>>> to detect changes in inode->i_crypt_info.  ceph_d_revalidate() is invoked
>>> but at that point I don't thing we have a way to know what is changing.
>>>
>>> Any ideas?
>> # ls mydir/
>> zy94Zt01M90xwYq+nxJsEvea+HYq49mqVgrUBkYrJAU
>> # ls mydir/zy94Zt01M90xwYq+nxJsEvea+HYq49mqVgrUBkYrJAU/
>> 24iNa8ICYc6nZZIkL,4n1sOtp9KiaTGtpq8PCZDQ6LU
>> ivG4rQYzg6YENagbTZaV2kh2sVouEdlkmBZPfgVDl48
>>
>> I have added the debug logs in all the places just like:
>>
>> @@ -784,7 +786,9 @@ static struct dentry *ceph_lookup(struct inode *dir, struct
>> dentry *dentry,
>>                  return ERR_PTR(-ENAMETOOLONG);
>>
>>          if (IS_ENCRYPTED(dir)) {
>> +       printk("%s fscrypt_has_encryption_key(dir): %d ======\n", __func__,
>> fscrypt_has_encryption_key(dir));
>>                  err = __fscrypt_prepare_readdir(dir);
>> +       printk("%s fscrypt_has_encryption_key(dir): %d ======\n", __func__,
>> fscrypt_has_encryption_key(dir));
>>                  if (err)
>>                          return ERR_PTR(err);
>>                  if (!fscrypt_has_encryption_key(dir)) {
>>
>>
>> # fscrypt unlock mydir
>> Enter custom passphrase for protector "l":
>> "mydir" is now unlocked and ready for use.
>>
>> And after "mydir/" was unlocked and then when doing:
>>
>> # touch mydir/dir/file2
>>
>> And when lookup the "dir/" dentry I can see the "mydir/" encryption key changed:
>>
>> 709 <7>[79125.023676] ceph:  __ceph_caps_issued_mask ino 0x10000000004 cap
>> 000000004dc11892 issued pAsLsXsFs (mask As)
>> 710 <7>[79125.023687] ceph:  __touch_cap 000000007071b095 cap 000000004dc11892
>> mds0
>> 711 <7>[79125.023823] ceph:  lookup 000000007071b095 dentry 00000000f97501b2
>> 'dir'
>> 712 <4>[79125.023838] ceph_lookup fscrypt_has_encryption_key(dir): 0 ======
>> 713 <4>[79125.024186] ceph_lookup fscrypt_has_encryption_key(dir): 1 ======
>> 714 <7>[79125.024194] ceph:   dir 000000007071b095 flags are 0x0
>> 715 <7>[79125.024269] ceph:  do_request on 00000000a93fafef
>>
>> I am thinking could we just make __fscrypt_prepare_readdir(), which will return
>> 0 when the key is already set or successfully set, to return 1 instead of 0 to
>> mark that the key changed ?
> OK, I see what you mean.  Thanks.  What about simply detect this change
> here instead of changing __fscrypt_prepare_readdir() semantics?  Because I
> think that would require changes in several other places, including other
> filesystems.
>
> What about something like this?
>
> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
> index edc2bf0aab83..499ec75d2496 100644
> --- a/fs/ceph/dir.c
> +++ b/fs/ceph/dir.c
> @@ -784,6 +784,8 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
>   		return ERR_PTR(-ENAMETOOLONG);
>   
>   	if (IS_ENCRYPTED(dir)) {
> +		bool had_key = fscrypt_has_encryption_key(dir);
> +
>   		err = __fscrypt_prepare_readdir(dir);
>   		if (err)
>   			return ERR_PTR(err);
> @@ -791,6 +793,8 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
>   			spin_lock(&dentry->d_lock);
>   			dentry->d_flags |= DCACHE_NOKEY_NAME;
>   			spin_unlock(&dentry->d_lock);
> +		} else if (!had_key) {
> +			__ceph_dir_clear_complete(ceph_inode(dir));
>   		}
>   	}
>   

Yeah. Could we just add one helper, such as:

bool ceph_fscrypt_prepare_readdir(dir)

{

     bool had_key = fscrypt_has_encryption_key(dir);

     err = __fscrypt_prepare_readdir(dir);

     if (!err && !had_key || err = -ENOKEY && had_key) {

         return true;   // key changed

     }

     return false;  // key not changed

}

Thanks!

- Xiubo

> Cheers,