linux-kernel - Re: [RFC PATCH] ceph: add support for encrypted snapshot names

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Date:   Fri, 25 Feb 2022 18:42:40 +0800
From:   Xiubo Li <xiubli@...hat.com>
To:     Luís Henriques <lhenriques@...e.de>
Cc:     Jeff Layton <jlayton@...nel.org>,
        Ilya Dryomov <idryomov@...il.com>, ceph-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] ceph: add support for encrypted snapshot names


On 2/25/22 5:48 PM, Luís Henriques wrote:
> Xiubo Li <xiubli@...hat.com> writes:
>
>> On 2/24/22 7:21 PM, Luís Henriques wrote:
>>> Since filenames in encrypted directories are already encrypted and shown
>>> as a base64-encoded string when the directory is locked, snapshot names
>>> should show a similar behaviour.
>>>
>>> Signed-off-by: Luís Henriques <lhenriques@...e.de>
>>> ---
>>>    fs/ceph/dir.c   | 15 +++++++++++++++
>>>    fs/ceph/inode.c | 10 +++++++++-
>>>    2 files changed, 24 insertions(+), 1 deletion(-)
>>>
>>> Support on the MDS for names that'll be > MAX_NAME when base64 encoded is
>>> still TBD.  I thought it would be something easy to do, but snapshots
>>> don't seem to make use of the CDir/CDentry (which is where alternate_name
>>> is stored on the MDS).  I'm still looking into this, but I may need some
>>> help there :-(
>>>
>>> Cheers,
>>> --
>>> Luís
>>>
>>> diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
>>> index a449f4a07c07..20ae600ee7cd 100644
>>> --- a/fs/ceph/dir.c
>>> +++ b/fs/ceph/dir.c
>>> @@ -1065,6 +1065,13 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
>>>    		op = CEPH_MDS_OP_MKSNAP;
>>>    		dout("mksnap dir %p snap '%pd' dn %p\n", dir,
>>>    		     dentry, dentry);
>>> +		/* XXX missing support for alternate_name in snapshots */
>>> +		if (IS_ENCRYPTED(dir) && (dentry->d_name.len >= 189)) {
>>> +			dout("encrypted snapshot name too long: %pd len: %d\n",
>>> +			     dentry, dentry->d_name.len);
>>> +			err = -ENAMETOOLONG;
>>> +			goto out;
>>> +		}
>>>    	} else if (ceph_snap(dir) == CEPH_NOSNAP) {
>>>    		dout("mkdir dir %p dn %p mode 0%ho\n", dir, dentry, mode);
>>>    		op = CEPH_MDS_OP_MKDIR;
>>> @@ -1109,6 +1116,14 @@ static int ceph_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
>>>    	    !req->r_reply_info.head->is_target &&
>>>    	    !req->r_reply_info.head->is_dentry)
>>>    		err = ceph_handle_notrace_create(dir, dentry);
>>> +
>>> +	/*
>>> +	 * If we have created a snapshot we need to clear the cache, otherwise
>>> +	 * snapshot will show encrypted filenames in readdir.
>>> +	 */
>> Do you mean dencrypted filenames ?
> What I see without this d_drop() is that, if I run an 'ls' in a snapshot
> directory immediately after creating it, the filenames in that snapshot
> will be encrypted.  Maybe there's a bug somewhere else and this d_drop()
> isn't the right fix...?

Maybe should fix this in ceph_fill_trace() in

        } else if ((req->r_op == CEPH_MDS_OP_LOOKUPSNAP ||... {

        }

?

I still haven't gotten where will encrypt it yet in mksnap case. Because 
the MDS will set the 'rinfo->head->is_target' but won't set the 
'rinfo->head->is_dentry', so in this case the dentry should keep the 
human readable name.

- Xiubo


> Cheers,