# Re: \[PATCH\] capabilities: Ambient capability set V1

- From: Serge E. Hallyn \<serge@hallyn.com\>
- Date: 2015-02-26 19:32:09 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2015/02/4438496
- Thread: https://ratatoskr.run/linux-api/2015/02/4426512/t.md

```text
On Thu, Feb 26, 2015 at 12:28:30PM -0600, Christoph Lameter wrote:
> On Thu, 26 Feb 2015, Serge E. Hallyn wrote:
> 
> > > Well doing that breaks su.
> >
> > Don't what exactly?  You're saying that doing
> >
> > pI' = pI
> > pA' = pA  (pA is ambient)
> > pP' = (X & fP) | (pI & (fI | pA))
> > pE' = pP' & (fE | pA)
> >
> > stopped su from having CAP_SETGID while
> >
> > pI' = pI
> > pA' = pA  (pA is ambient)
> > pP' = (X & fP) | (pI & (fI | pA))
> > pE' = pP' & fE
> >
> > worked?  I'll hope you're saying both "fail", in which case
> 
> fE does not exist in cpu_vfs_cap_data. We only get fI and fP. Why in the
> world does setcap allow setting fE?

It sets a bit in the magic_etc.  So fE is either all on or all off.

> V1 does not use fE. In my newer attempt, I seemed to have worked
> with zeroed field that I assumed was filled in.
> 
> I will just do
> 
> pE' = pP'
> 
> Ok?

Andrew Morgan was against that.  What if we changed

pE' = pP' & (fE | pA)

to

	if (pA)
		pE' = pP' & fE
	else
		pE' = pP'

```