Re: [PATCH] in-core AFS multiplexor and PAG support

[David Howells <dhowells@warthog.cambridge.redhat.com>]

Linus Torvalds wrote:
> On Tue, 13 May 2003, David Howells wrote:
> > 
> >  (1) PAG (Process Authentication Group) support. A PAG is ID'd by a unique
> >      number, and is represented in memory as a structure that has a ring of
> >      associated authentication tokens.
> > 
> >      Each process can either be part of a PAG, or it can PAG-less - in
> >      which case it has no authentication tokens.
> > 
> >      Two new syscalls are added: setpag and getpag.
> 
> I think the code looks pretty horrible,

Any particular bits?

> but I think we'll need something like this to keep track of keys. However,
> I'm not sure we should make this a new structure - I think we should make
> the current "tsk->user" thing _be_ the "PAG".

Maybe... There are arguments either way, but if the token ring is kept in
struct user, a task can't detach from it and pass a token-less set of keys
onto another process it wants to run.

Also, using a separate PAG structure means that you can lend your keys to an
SUID program and conversely it means a SUID program can't so easily gain
access to keys it didn't inherit from its caller.

I'm not sure that the ability to arbitrarily join a PAG should be permitted,
but it was requested.

David