[PATCH] cifs: Support for an upcall to map SID to an uid and a gid

[Jeff Layton]

On Sat, 11 Dec 2010 19:57:11 -0500
Richard Sharpe <realrichardsharpe at gmail.com> wrote:

> On Sat, Dec 11, 2010 at 7:30 PM, Jeff Layton <jlayton at samba.org> wrote:
> >>
> >> Will look into this.  One thing that concerns me is if a cached etnry
> >> for a SID with its name and an id (either an uid or a gid), if that SID
> >> now represents a different object and has differernt name, would
> >> not cached info be incorrect?  Not sure if this can ever happen
> >> or how would it happen and if it does, what would be a trigger
> >> for a cache revalidation and purges!
> >>
> >
> > Sure, mappings can change. But, you still have the same problem with
> > what you're proposing in these patches. The userspace program isn't
> > setting a timeout on the key. Once a mapping is put in the keyring,
> > it's there until it's revoked. You probably want to set a max TTL for
> > the entries in the cache regardless of what scheme is used.
> 
> I was under the impression that SIDs are never reused. Perhaps I am mistaken.
> 

That may be, but the mapping of a SID is dependent upon settings in
config files that could change. It seems reasonable to me to only cache
these mappings for a period of time in the event that they do. That
period of time could default to being rather long and be tunable.

-- 
Jeff Layton <jlayton at samba.org>