Re: [PATCH] nvme-tcp: Check if request has started before processing it

[Hannes Reinecke]

On 2/12/21 10:49 PM, Sagi Grimberg wrote:
> > > > blk_mq_tag_to_rq() will always return a request if the command_id is
> > > > in the valid range. Check if the request has been started. If we
> > > > blindly process the request we might double complete a request which
> > > > can be fatal.
> > >
> > > How did you get to this one? did the controller send a completion for
> > > a completed/bogus request?
> >
> > If that is the case, then that must mean it's possible the driver could
> > have started the command id just before the bogus completion check. Data
> > iorruption, right?
>
> Yes, which is why I don't think this check is very useful..

I actually view that as a valid protection against spoofed frames.
Without it it's easy to crash the machine by injecting fake completions 
with random command ids.

Cheers,

Hannes
--
Dr. Hannes Reinecke                Kernel Storage Architect
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