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

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Date:   Wed, 10 Apr 2019 14:21:31 -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 20:37:55 +0300
Andriy Shevchenko <andriy.shevchenko@...ux.intel.com> wrote:

> On Tue, Apr 09, 2019 at 09:43:28AM -0700, Jacob Pan wrote:
> > 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:  
> 
> > > > +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  
> 
> I hardly see any of these applied to your case here.
> Care to show what I'm missing?
> 
I thought your comments was that I should not need to initialize local
variable ret = 0. Always initialize local variable can be a good
security practice as suggested in the paper. Perhaps I missed
something :)
> > > > +	if (unlikely(!domain->ops->cache_invalidate))
> > > > +		return -ENODEV;
> > > > +
> > > > +	ret = domain->ops->cache_invalidate(domain, dev,
> > > > inv_info); +
> > > > +	return ret;
> > > > +}    
> 

[Jacob Pan]