Re: [PATCH] capabilities: Ambient capability set V1

[Serge Hallyn <serge.hallyn@ubuntu.com>]

Quoting Christoph Lameter (cl@linux.com):
> On Tue, 24 Feb 2015, Serge Hallyn wrote:
> 
> > Unless I'm misunderstanding what you are saying, apps do have surprises.
> > They drop capabilities, execute a file, and the result has capabilities
> > which the app couldn't have expected.  At least if the bits have to be
> > in fI to become part of pP', the app has a clue.
> 
> Well yes but the surprises do not occur in the cap bits they are
> manipulating or inspecting via prctl.
> 
> > To be clear, I'm suggesting that the rules at exec become:
> >
> > pI' = pI
> 
> Ok that is new and on its own may solve the issue?

No that's not new.

> > pA' = pA  (pA is ambient)
> 
> Thats what this patch does
> 
> > pP' = (X & fP) | (pI & (fI | pA))
> 
> Hmmm... fP is empty for the file not having caps. so
> 
> pP' = pI & pA

Right.

> > pE' = pP' & fE
> 
> fE? So the inherited caps are not effective? fE would be empty for a file
> not having caps thus the ambient caps would not be available in the child.

Yeah we could make this

pE' = pP' & (fE | pA)

-serge