linux-kernel - Re: [PATCH 08/18] iommu: Introduce cache

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Message-ID: <20190409094328.03731c3c@jacob-builder>
Date:   Tue, 9 Apr 2019 09:43:28 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Andriy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jean-Philippe Brucker <jean-philippe.brucker@....com>,
        Yi Liu <yi.l.liu@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        "Liu, Yi L" <yi.l.liu@...ux.intel.com>, Liu@...le.fi.intel.com,
        Eric Auger <eric.auger@...hat.com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH 08/18] iommu: Introduce cache_invalidate API

On Tue, 9 Apr 2019 13:07:18 +0300
Andriy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Mon, Apr 08, 2019 at 04:59:23PM -0700, Jacob Pan wrote:
> > From: "Liu, Yi L" <yi.l.liu@...ux.intel.com>
> > 
> > In any virtualization use case, when the first translation stage
> > is "owned" by the guest OS, the host IOMMU driver has no knowledge
> > of caching structure updates unless the guest invalidation
> > activities are trapped by the virtualizer and passed down to the
> > host.
> > 
> > Since the invalidation data are obtained from user space and will be
> > written into physical IOMMU, we must allow security check at various
> > layers. Therefore, generic invalidation data format are proposed
> > here, model specific IOMMU drivers need to convert them into their
> > own format.  
> 
> > +int iommu_cache_invalidate(struct iommu_domain *domain, struct
> > device *dev,
> > +			   struct iommu_cache_invalidate_info
> > *inv_info) +{
> > +	int ret = 0;  
> 
> Redundant assignment.
> 
I am not a security expert but initialization of local variable can be
more secure.
I was looking at this talk.
https://outflux.net/slides/2018/lss/danger.pdf
https://cwe.mitre.org/data/definitions/457.html

> > +
> > +	if (unlikely(!domain->ops->cache_invalidate))
> > +		return -ENODEV;
> > +
> > +	ret = domain->ops->cache_invalidate(domain, dev, inv_info);
> > +
> > +	return ret;
> > +}  
> 

[Jacob Pan]