linux-kernel - Re: [PATCH v4 14/23] iommufd: Add mmap interface

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Message-ID: <20250516132956.GI613512@nvidia.com>
Date: Fri, 16 May 2025 10:29:56 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: "Tian, Kevin" <kevin.tian@...el.com>
Cc: Nicolin Chen <nicolinc@...dia.com>, "corbet@....net" <corbet@....net>,
	"will@...nel.org" <will@...nel.org>,
	"bagasdotme@...il.com" <bagasdotme@...il.com>,
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	"Liu, Yi L" <yi.l.liu@...el.com>,
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	"zhangzekun11@...wei.com" <zhangzekun11@...wei.com>,
	"iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
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Subject: Re: [PATCH v4 14/23] iommufd: Add mmap interface

On Fri, May 16, 2025 at 04:08:25AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@...dia.com>
> > Sent: Friday, May 16, 2025 12:47 AM
> > 
> > On Thu, May 08, 2025 at 08:02:35PM -0700, Nicolin Chen wrote:
> > > +	/* vma->vm_pgoff carries an index to an mtree entry (immap) */
> > > +	immap = mtree_load(&ictx->mt_mmap, vma->vm_pgoff);
> > > +	if (!immap)
> > > +		return -ENXIO;
> > > +	if (length >> PAGE_SHIFT != immap->num_pfns)
> > > +		return -ENXIO;
> > 
> > This needs to validate that vm_pgoff is at the start of the immap or
> > num_pfns is the wrong thing to validate length against.
> > 
> 
> vm_pgoff is the index into mtree. If it's wrong mtree_load() will
> fail already?

I'm not sure? I thought mtree_load will return any range that
intersects with the given index?

Otherwise what is the point of having a range based datastructure?

Jason