Date: Sat, 11 Jul 2015 03:17:36 -0700
From: "'Christoph Hellwig'" <hch@infradead.org>
To: Jason Gunthorpe <jgunthorpe@obsidianresearch.com>
Cc: Tom Talpey <tom@talpey.com>, Doug Ledford <dledford@redhat.com>,
        "'Christoph Hellwig'" <hch@infradead.org>,
        Sagi Grimberg <sagig@dev.mellanox.co.il>,
        Steve Wise <swise@opengridcomputing.com>, sagig@mellanox.com,
        ogerlitz@mellanox.com, roid@mellanox.com, linux-rdma@vger.kernel.org,
        eli@mellanox.com, target-devel@vger.kernel.org,
        linux-nfs@vger.kernel.org, trond.myklebust@primarydata.com,
        bfields@fieldses.org, Oren Duer <oren@mellanox.com>
Subject: Re: [PATCH V3 1/5] RDMA/core: Transport-independent access flags
Message-ID: <20150711101736.GA14741@infradead.org>
References: <20150708190842.GB11740@obsidianresearch.com>
 <20150708203205.GA21847@infradead.org>
 <20150709000337.GE16812@obsidianresearch.com>
 <559EF332.7060103@redhat.com>
 <20150709225306.GA30741@obsidianresearch.com>
 <559FC710.1050307@talpey.com>
 <20150710161108.GA19042@obsidianresearch.com>
 <55A00754.4010009@redhat.com>
 <55A01225.9000000@talpey.com>
 <20150710195420.GA31500@obsidianresearch.com>
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In-Reply-To: <20150710195420.GA31500@obsidianresearch.com>
Sender: linux-nfs-owner@vger.kernel.org

On Fri, Jul 10, 2015 at 01:54:20PM -0600, Jason Gunthorpe wrote:
> diff --git a/drivers/infiniband/core/verbs.c b/drivers/infiniband/core/verbs.c
> index bac3fb406a74..6ed7e0f6c162 100644
> --- a/drivers/infiniband/core/verbs.c
> +++ b/drivers/infiniband/core/verbs.c
> @@ -1126,6 +1126,12 @@ struct ib_mr *ib_get_dma_mr(struct ib_pd *pd, int mr_access_flags)
>         struct ib_mr *mr;
>         int err;
>  
> +       /* Granting remote access to the physical MR is a security hole, don't
> +          do it. */
> +       WARN_ON_ONCE(mr_access_flags &
> +               (IB_ACCESS_REMOTE_WRITE | IB_ACCESS_REMOTE_READ |
> +                IB_ACCESS_REMOTE_ATOMIC));
> +

How about providing a system-wide IB_ACCESS_LOCAL_READ |
IB_ACCESS_LOCAL_WRITE MR that all drivers can use and get rid of
ib_get_dma_mr in the long run?  That would help to nicely simplify
drivers?

Currently various drivers are using ib_get_dma_mr with remote flags
unfortunately, e.g. the SRP initiator driver uses it to optimize away
memory registrtions for single SGL entry requests.  That looks fixable
realtively easily, but I don't understand the other consumers as good.