RE: [PATCH v2 1/2] VT-d: avoid NULL deref on domain_context_mapping_one() error paths

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Thursday, April 7, 2022 3:50 PM
> 
> On 07.04.2022 09:41, Roger Pau Monné wrote:
> > On Thu, Apr 07, 2022 at 08:11:06AM +0200, Jan Beulich wrote:
> >> First there's a printk() which actually wrongly uses pdev in the first
> >> place: We want to log the coordinates of the (perhaps fake) device
> >> acted upon, which may not be pdev.
> >>
> >> Then it was quite pointless for eb19326a328d ("VT-d: prepare for per-
> >> device quarantine page tables (part I)") to add a domid_t parameter to
> >> domain_context_unmap_one(): It's only used to pass back here via
> >> me_wifi_quirk() -> map_me_phantom_function(). Drop the parameter
> again.
> >>
> >> Finally there's the invocation of domain_context_mapping_one(), which
> >> needs to be passed the correct domain ID. Avoid taking that path when
> >> pdev is NULL and the quarantine state is what would need restoring to.
> >> This means we can't security-support PCI devices with RMRRs (if such
> >> exist in practice) any longer.
> >
> > The sentence:
> >
> > "This means we can't security-support PCI devices with RMRRs"
> >
> > Seems too broad and could lead to confusion. So I would maybe use:
> > "legacy PCI devices" or "non PCI Express devices".
> 
> Right. I did actually forget to either drop or edit that sentence. I've
> now extended this to
> 
> "This means we can't security-support non-PCI-Express devices with RMRRs
>  (if such exist in practice) any longer; note that as of trhe 1st of the
>  two commits referenced below assigning them to DomU-s is unsupported
>  anyway."
> 

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>