linux-kernel - Re: [Xen-devel] [PATCH V3 6/6]: PVH:privcmd changes.

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Date:	Thu, 18 Oct 2012 17:02:23 -0700
From:	Mukesh Rathor <mukesh.rathor@...cle.com>
To:	Ian Campbell <Ian.Campbell@...rix.com>
Cc:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"Xen-devel@...ts.xensource.com" <Xen-devel@...ts.xensource.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH V3 6/6]: PVH:privcmd changes.

On Thu, 18 Oct 2012 11:35:53 +0100
Ian Campbell <Ian.Campbell@...rix.com> wrote:

> 
> > @@ -439,6 +490,19 @@ static long privcmd_ioctl(struct file *file,
> >  	return ret;
> >  }
> >  
> > +static void privcmd_close(struct vm_area_struct *vma)
> > +{
> > +	struct page **pages = vma ? vma->vm_private_data : NULL;
> 
> Can VMA really be NULL?...

Good programming I thought!

> > +	int numpgs = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
> 
> ...I assume not since you unconditionally dereference it here.

Added this later, and just didn't change the earlier part.

> > +	if (!pages || !numpgs
> > || !xen_feature(XENFEAT_auto_translated_physmap))
> 
> In the non-xlat case pages will (or should!) be 1 here which will pass
> the first clause of the test.
> 
> Although the later clauses will catch this I think it would be worth
> ordering the checks such that they are each valid, perhaps by pulling
> the feature check to the front or by separating the !xlat case from
> the other two which are valid iff xlat == True.
> 

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