[PATCH v3] nvme: fix memory corruption for passthrough metadata

[Kanchan Joshi]

On 10/11/2023 10:32 AM, Christoph Hellwig wrote:
>> Just that I was not sure on (i) whether to go back that far in
>> history, and (ii) what patch to tag.
> 
> I think the one that adds the original problem is:
> 
> 63263d60e0f9f37bfd5e6a1e83a62f0e62fc459f
> Author: Keith Busch <kbusch at kernel.org>
> Date:   Tue Aug 29 17:46:04 2017 -0400
> 
>      nvme: Use metadata for passthrough commands

Thanks.

> 
>>>> +     /* Exclude commands that do not have nlb in cdw12 */
>>>> +     if (!nvme_nlb_in_cdw12(c->common.opcode))
>>>> +             return true;
>>>
>>> So we can still get exactly the same corruption for all commands that
>>> are not known?  That's not a very safe way to deal with the issue..
>>
>> Given the way things are in NVMe, I do not find a better way.
>> Maybe another day for commands that do (or can do) things very
>> differently for nlb and PI representation.
> 
> Fixing just a subset of these problems is pointless.  If people want
> to use metadata on vendor specific commands they need to work with
> NVMe to figure out a generic way to pass the length.

Do you suggest that vendor specific opcodes should be blocked here?