Re: [Xen-devel] [PATCH v2] domctl: relax getdomaininfo permissions

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 08/11/2016 07:33 AM, Jan Beulich wrote:
> > > > On 05.08.16 at 13:20, <JBeulich@xxxxxxxx> wrote:
> Daniel,
>
> I've only now realized that I forgot to Cc you on this v2.
>
> Jan
>
> > Qemu needs access to this for the domain it controls, both due to it
> > being used by xc_domain_memory_mapping() (which qemu calls) and the
> > explicit use in hw/xenpv/xen_domainbuild.c:xen_domain_poll(). Extend
> > permissions to that of any "ordinary" domctl: A domain controlling the
> > targeted domain can invoke this operation for that target domain (which
> > is being achieved by no longer passing NULL to xsm_domctl()).
> >
> > This at once avoids a for_each_domain() loop when the ID of an
> > existing domain gets passed in.
> >
> > Reported-by: Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>

[...]
> I know there had been an alternative patch suggestion, but that one
> doesn't seem have seen a formal submission so far, so here is my
> original proposal.
>
> I wonder what good the duplication of the returned domain ID does: I'm
> tempted to remove the one in the command-specific structure. Does
> anyone have insight into why it was done that way?
>
> I further wonder why we have XSM_OTHER: The respective conversion into
> other XSM_* values in xsm/dummy.h could as well move into the callers,
> making intentions more obvious when looking at the actual code.
The XSM_* values are not actually present in the XSM hook functions, so
they have to be a static value per function.  Otherwise, the dummy XSM
module won't have enough information to make the same decision as the
inlined dummy.h version does.

An alternate solution would be to add an explicit action parameter to
the hooks that currently use XSM_OTHER, but that mostly just moves the
conversion switch statement around and adds a pointless computation in
the case when the parameter is not used.


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