On Mon, 2005-11-28 at 12:06 -0500, Trond Myklebust wrote:
> On Mon, 2005-11-28 at 11:48 -0600, Steve French wrote:
> > Why are there no calls to inode_change_ok in nfs (on the client), but
> > there are in most other filesytsems? Seems like there are some cases
> > in nfs in which a local permission check is done via a call to
> > nfs_permission which calls generic_permission ... if that is the case
> > why not do a call to inode_change_ok in similar cases?
>
> Under the NFS model, the server manages the permissions, not the client.
>
> The purpose of inode_change_ok() is to perform a load of local checks
> which are simply alien to that model:
>
> a) your capabilities don't mean anything to the server. Its decision to
> grant the ability to change owner of a file is based on your
> credentials, not your capabilities.
>
> b) Even the uid/gid checks don't take into account the fact that the
> server may be mapping you into different users/groups (c.f. root
> squashing etc.).
>
> All, in all, a call to inode_change_ok() would at best be redundant, and
> at worst, be plain incorrect.
BTW: The call to permission() is thoroughly redundant too, and really
wants to be optimised away. Permissions checking is done by the server
on the actual SETATTR RPC call...
Cheers,
Trond
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