linux-kernel - Re: [PATCH v4 2/2] iommu/sva: Remove mm parameter from SVA bind API

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Date:   Wed, 12 May 2021 12:24:26 +0200
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Christoph Hellwig <hch@...radead.org>,
        Yi Liu <yi.l.liu@...el.com>, Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Dave Jiang <dave.jiang@...el.com>, wangzhou1@...ilicon.com,
        zhangfei.gao@...aro.org, vkoul@...nel.org
Subject: Re: [PATCH v4 2/2] iommu/sva: Remove mm parameter from SVA bind API

On Mon, May 10, 2021 at 06:25:08AM -0700, Jacob Pan wrote:
> The mm parameter in iommu_sva_bind_device() is intended for privileged
> process perform bind() on behalf of other processes. This use case has
> yet to be materialized, let alone potential security implications of
> adding kernel hooks without explicit user consent.
> In addition, with the agreement that IOASID allocation shall be subject
> cgroup limit. It will be inline with misc cgroup proposal if IOASID
> allocation as part of the SVA bind is limited to the current task.
> 
> Link: https://lore.kernel.org/linux-iommu/20210303160205.151d114e@jacob-builder/
> Link: https://lore.kernel.org/linux-iommu/YFhiMLR35WWMW%2FHu@myrica/
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>

I'm not particularly enthusiastic about this change, because restoring the
mm parameter will be difficult after IOMMU drivers start assuming
everything is on current. Regardless, it looks correct and makes my life
easier (and lightens my test suite quite a bit).

Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>