[PATCH v2 4/4] nvme: code command_id with a genctr for use-after-free validation

[Chaitanya Kulkarni]

On 5/25/21 17:45, Keith Busch wrote:
>> The bad controller should be fixed.
>>
>> In the past, I've sent patches that check that sqid match in nvme cqe to
>> protect faulty drives that might send
>> the completion on a wrong msix.
>>
>> My patch wasn't accepted since it added an additional "if" in the fast path.
>>
>> Now we're adding much more operation in the fast path because of buggy ctrl
>> ?
> I shared the same performance concern on v1 on this series. I haven't
> been able to test this one yet (only have emulation for two more weeks).
>
> Hannes says the bug this catches happens frequently enough on TCP. If we
> don't catch it, we get kernel panic or corruption, so we defintely need to
> do something. Sagi correctly noted this type of bug is not unique to TCP
> (or even NVMe, for that matter), but if there is a performance impact on
> PCI, and no one so far reports such an issue, I would still recommend
> this type of mitigation be isolated to transports that actually observe
> invalid CQEs.
>  

Please do that if possible.