Re: [PATCH v3] x86/mce: retrieve poison range from hardware

[Luck, Tony]

On Mon, Jul 18, 2022 at 09:11:33PM +0000, Jane Chu wrote:
> On 7/18/2022 12:22 PM, Luck, Tony wrote:
> >> It appears the kernel is trusting that ->physical_addr_mask is non-zero
> >> in other paths. So this is at least equally broken in the presence of a
> >> broken BIOS. The impact is potentially larger though with this change,
> >> so it might be a good follow-on patch to make sure that
> >> ->physical_addr_mask gets fixed up to a minimum mask value.
> > 
> > Agreed. Separate patch to sanitize early, so other kernel code can just use it.
> > 
> 
> Is it possible that with
>    if (mem->validation_bits & CPER_MEM_VALID_PA_MASK)
> the ->physical_addr_mask is still untrustworthy?

The validation_bits just show which fields the BIOS *says* it filled in.
If a validation bit isn't set, then Linux should certainly ignore that
field. But if it is set, then Linux needs to decide whether to use the
value, or do a sanity check first.

-Tony