Re: [PULL 06/30] spapr: Do PHB hoplug sanity check at pre-plug

[Peter Maydell]

On Mon, 14 Dec 2020 at 04:58, David Gibson <david@gibson.dropbear.id.au> wrote:
>
> From: Greg Kurz <groug@kaod.org>
>
> We currently detect that a PHB index is already in use at plug time.
> But this can be decteted at pre-plug in order to error out earlier.
>
> This allows to pass &error_abort to spapr_drc_attach() and to end
> up with a plug handler that doesn't need to report errors anymore.
>
> Signed-off-by: Greg Kurz <groug@kaod.org>
> Message-Id: <20201120234208.683521-8-groug@kaod.org>
> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

Hi; this change seems to have nudged one of Coverity's
heuristics into deciding that spapr_drc_by_id() can return
NULL (because its return value is checked here, I suspect),
so it reports CID 1437757, 1437758, where spapr_add_lmbs()
and spapr_memory_unplug_request() both take the return value
of spapr_drc_by_id() and pass it directly to spapr_drc_index(),
which will crash if it is passed a NULL pointer.

Is it impossible for spapr_drc_by_id() to return NULL in
those functions (ie Coverity false positive) or is there
a missing error check ?

thanks
-- PMM