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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

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".

> 
> Fixes: 8f41e481b485 ("VT-d: re-assign devices directly")
> Fixes: 14dd241aad8a ("IOMMU/x86: use per-device page tables for quarantining")
> Coverity ID: 1503784
> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>

Thanks, Roger.