netdev - Re: net/smc and the RDMA core

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Message-ID: <20170504084825.GA5399@lst.de>
Date:   Thu, 4 May 2017 10:48:25 +0200
From:   "hch@....de" <hch@....de>
To:     Sagi Grimberg <sagi@...mberg.me>
Cc:     Bart Van Assche <Bart.VanAssche@...disk.com>,
        "hch@....de" <hch@....de>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "ubraun@...ux.vnet.ibm.com" <ubraun@...ux.vnet.ibm.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>
Subject: Re: net/smc and the RDMA core

On Thu, May 04, 2017 at 11:43:50AM +0300, Sagi Grimberg wrote:
> I would also suggest that you stop exposing the DMA MR for remote
> access (at least by default) and use a proper reg_mr operations with a
> limited lifetime on a properly sized buffer.

Yes, exposing the default DMA MR is a _major_ security risk.  As soon
as SMC is enabled this will mean a remote system has full read/write
access to the local systems memory.

There іs a reason why I removed the ib_get_dma_mr function and replaced
it with the IB_PD_UNSAFE_GLOBAL_RKEY key that has _UNSAFE_ in the name
and a very long comment explaining why, and I'm really disappointed that
we got a driver merged that instead of asking on the relevant list on
why a change unexpertong a function it needed happened and instead
tried the hard way to keep a security vulnerarbility alive.