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

[Jan Beulich <jbeulich@xxxxxxxx>]

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."

>> 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.

Jan