[PATCH v3 4/4] fuse: define the filesystem as untrusted

[Stef Bon]

2018-03-14 22:42 GMT+01:00 Eric W. Biederman <ebiederm at xmission.com>:
>>
>> Please tell me if I'm hijacking the thread.
>
> Unless something brings us to non-consensus about the patches to merge
> we are good.  I think this is an area that need some discussion.
>
> The big big thing right now, as I understand it, is these mechanisms that
> nfs uses to keep the cache in sync are not clearly reflected in the vfs
> in a way that ima can take advantage of them.
>
>

Chuck you mean fschange notifications methods like
NT_TRANSACT_NOTIFY_CHANGE for cifs. I believe that NFS4 has something simular.
These mechanism will inform the client when a file in a watched
directory is changed.
This is not yet supported in Linux (these methods are not triggered
any way when setting a watch using inotify for exmple).
There was support with dnotify
(https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/fs/cifs/cifssmb.c#n6393).

But these methods are triggered by the user and not the VFS/kernel and
therefore cannot garantee that all files on the client
are the same as on the server.
This also counts for a read delegation with nfs and methods like
leases in a client server environment.

Stef
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