[openib-general] mthca FMR correctness (and memory windows)

[Diego Crupnicoff]

> >
> >Can you elaborate on the issue of fungibility?  If one entity has two
> >QPs, one of which it's using for traffic and one of which it's using
> >for MW binds, I don't see any security issue (beyond the fact that
> >you've now given up ordering of operations between the QPs).
> 
> If I can snoop or guess rkeys (not a huge challenge with 32 bits), and
> if I can use them on an arbitrary queuepair, then I can handily peek and
> poke at memory that does not belong to me.

No. You can't get to the Window from an arbitrary QP. Only from those QPs
that belong to the same PD.

> 
> For this reason, iWARP requires its steering tags to be scoped to a single
> connection. This leverages the IP security model and provides correctness.
> 
> It is true that IB implementations generally don't do this. They should.

IB allows the 2 flavors (PD bound Windows aka type 1, and QP bound Windows
aka type 2).

> 
> Tom.
> 
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