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

Jason Gunthorpe
2025-05-16T13:30:00Z

On Fri, May 16, 2025 at 04:08:25AM +0000, Tian, Kevin wrote:
> > From: Jason Gunthorpe <jgg@nvidia.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