Jeff Layton <jlayton@xxxxxxxxxx> writes: > On Thu, 2022-03-17 at 11:11 +0000, Luís Henriques wrote: >> Xiubo Li <xiubli@xxxxxxxxxx> writes: >> >> > On 3/17/22 6:01 PM, Jeff Layton wrote: >> > > I'm not sure we want to worry about .snap directories here since they >> > > aren't "real". IIRC, snaps are inherited from parents too, so you could >> > > do something like >> > > >> > > mkdir dir1 >> > > mkdir dir1/.snap/snap1 >> > > mkdir dir1/dir2 >> > > fscrypt encrypt dir1/dir2 >> > > >> > > There should be nothing to prevent encrypting dir2, but I'm pretty sure >> > > dir2/.snap will not be empty at that point. >> > >> > If we don't take care of this. Then we don't know which snapshots should do >> > encrypt/dencrypt and which shouldn't when building the path in lookup and when >> > reading the snapdir ? >> >> In my patchset (which I plan to send a new revision later today, I think I >> still need to rebase it) this is handled by using the *real* snapshot >> parent inode. If we're decrypting/encrypting a name for a snapshot that >> starts with a '_' character, we first find the parent inode for that >> snapshot and only do the operation if that parent is encrypted. >> >> In the other email I suggested that we could prevent enabling encryption >> in a directory when there are snapshots above in the hierarchy. But now >> that I think more about it, it won't solve any problem because you could >> create those snapshots later and then you would still need to handle these >> (non-encrypted) "_name_xxxx" snapshots anyway. >> > > Yeah, that sounds about right. > > What happens if you don't have the snapshot parent's inode in cache? > That can happen if you (e.g.) are running NFS over ceph, or if you get > crafty with name_to_handle_at() and open_by_handle_at(). > > Do we have to do a LOOKUPINO in that case or does the trace contain that > info? If it doesn't then that could really suck in a big hierarchy if > there are a lot of different snapshot parent inodes to hunt down. > > I think this is a case where the client just doesn't have complete > control over the dentry name. It may be better to just not encrypt them > if it's too ugly. I *think* this is covered by my last revision. I didn't really tested NFS, but this was why the patches are using ceph_get_inode() and falling back to ceph_find_inode(). I tested this by directly mounting an encrypted directory that had snapshots from a realm that wasn't in the mount root. (Obviously, these snapshot names are *not* encrypted because they belong to snapshots that are not encrypted either.) Cheers, -- Luís > Another idea might be to just use the same parent inode (maybe the > root?) for all snapshot names. It's not as secure, but it's probably > better than nothing. > -- > Jeff Layton <jlayton@xxxxxxxxxx>
