On Thu, Feb 26, 2015 at 12:51:57PM -0800, Andy Lutomirski wrote:
> On Thu, Feb 26, 2015 at 12:34 PM, Serge E. Hallyn <serge@xxxxxxxxxx> wrote:
> > On Thu, Feb 26, 2015 at 02:13:00PM -0600, Christoph Lameter wrote:
> >> On Thu, 26 Feb 2015, Serge E. Hallyn wrote:
> >>
> >> > Andrew Morgan was against that. What if we changed
> >> >
> >> > pE' = pP' & (fE | pA)
> >> >
> >> > to
> >> >
> >> > if (pA)
> >> > pE' = pP' & fE
> >> > else
> >> > pE' = pP'
> >> >
> >>
> >> Same problem as before. The ambient bits will not be set in pE'.
> >
> > And what if I weren't scatterbrained and we did
> >
> > if (pA)
> > pE' = pP'
> > else
> > pE' = pP' & fE
> >
> > All pP' bits would be set in pE'.
>
> That seems reasonable to me, except for my paranoia:
>
> What if there's a program with CAP_DAC_OVERRIDE in fP and fE set to
> the empty set (i.e. the magic effective bit cleared), and the program
> relies on that. A malicious user has CAP_NET_BIND and sets pA =
> CAP_NET_BIND. Boom!
>
> If we changed that to if (pA') and zeroed pA if fP is non-empty then
> this problem goes away.
Hm, the problem is that then the empty pA is inherited by children.
I do see that any program with fP set should probably run with only
what it requested. Would
if (pA && is_empty(fP))
pE' = pP'
else
pE' = pP' & fE
help? Or are you worried about a program with fP set which then
executes other programs?
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