linux-kernel - Re: [PATCH] vfio: fix VFIO_IOMMU_UNMAP_DMA when end of range would overflow u64

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Message-ID: <20251006225039.GA3441843@ziepe.ca>
Date: Mon, 6 Oct 2025 19:50:39 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Alex Mastro <amastro@...com>
Cc: Alex Williamson <alex.williamson@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vfio: fix VFIO_IOMMU_UNMAP_DMA when end of range would
 overflow u64

On Mon, Oct 06, 2025 at 09:29:07AM -0700, Alex Mastro wrote:
> On Mon, Oct 06, 2025 at 09:16:18AM -0300, Jason Gunthorpe wrote:
> > This doesn't seem complete though, if the range ends at the ULONG_MAX
> > then these are not working either:
> > 
> > 		if (start < dma->iova + dma->size) {
> > 
> > ?
> > 
> > And I see a few more instances like that eg in
> > vfio_iova_dirty_bitmap(), vfio_dma_do_unmap(), vfio_iommu_replay()
> 
> You are right. There are several places which would need to be fixed to handle
> mappings which lie against the end of the addressable range. At least these
> would need to be vetted:

Could we block right at the ioctl inputs that end at ULONG_MAX? Maybe
that is a good enough fix?

Jason