Re: inode_change_ok

[Trond Myklebust]

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.

Cheers,
  Trond

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