Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags

Jason Gunthorpe
2015-07-10T20:48:34Z

On Fri, Jul 10, 2015 at 01:54:20PM -0600, Jason Gunthorpe wrote:
> On Fri, Jul 10, 2015 at 02:42:45PM -0400, Tom Talpey wrote:
>
> > >>For the proposed iSER patch the problem is very acute, iser makes a
> > >>single PD and phys MR at boot time for each device. This means there
> > >>is a single machine wide unchanging rkey that allows remote physical
> > >>memory access. An attacker only has to repeatedly open QPs to iSER and
> > >>guess rkey values until they find it. Add in likely non-crypto
> > >>randomness for rkeys, and I bet it isn't even that hard to do.
> >
> > The rkeys have a PD, wich cannot be forged, so it's not a matter of
> > attacking, but it is most definitely a system integrity risk, as I
> > mentioned earlier, a simple arithmetic offset mistake can overwrite
> > anything.
>
> Can you explain this conclusion?

Okay, so I see, iser is client only, it doesn't create a listening QP,
so you have to trick it into connecting to a malicious server, and
that is just a trust issue as Doug points out. Presumably this patch
doesn't impact isert?

But what about NFS? It looks to me like all of the ib_get_dma_mr
calls in NFS have the possibility of having IB_ACCESS_REMOTE_WRITE
set, but only on older adaptors?

Jason