linux-kernel - Re: [PATCH v2 1/3] vfio/type1: sanitize for overflow using check_*

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Message-ID: <aObjW9VxYMkFQ1KB@devgpu015.cco6.facebook.com>
Date: Wed, 8 Oct 2025 15:19:07 -0700
From: Alex Mastro <amastro@...com>
To: Jason Gunthorpe <jgg@...pe.ca>
CC: Alex Williamson <alex.williamson@...hat.com>,
        Alejandro Jimenez
	<alejandro.j.jimenez@...cle.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] vfio/type1: sanitize for overflow using
 check_*_overflow

On Wed, Oct 08, 2025 at 08:39:21AM -0700, Alex Mastro wrote:
> On Wed, Oct 08, 2025 at 09:19:30AM -0300, Jason Gunthorpe wrote:
> > On Tue, Oct 07, 2025 at 09:08:46PM -0700, Alex Mastro wrote:
> > > +	if (check_add_overflow(user_iova, iova_size - 1, &iova_end))
> > > +		return -EINVAL;
> > 
> > Let's be consistent with iommufd/etc, 'end' is start+size 'last' is start+size-1
> > 
> > Otherwise it is super confusing :(
> 
> 
> Both suggestions SGTM.

I'm not sure about the latter anymore. There's somewhat pervasive precedent for
using 'end' as the inclusive limit in vfio_iommu_type1.c. I am all for making
things less confusing. I don't think I can introduce 'end' 'last' convention
without preparing the existing code first.

Thoughts? Spend another commit renaming this to 'last'? Tolerate inconsistency
between vfio and iommufd?

116  struct vfio_iova {
117          struct list_head        list;
118          dma_addr_t              start;
119          dma_addr_t              end;
120  };
...
2037                  end = resv->start + resv->length - 1;
2038
2039                  list_for_each_entry_safe(n, next, iova, list) {
2040                          int ret = 0;
2041
2042                          /* No overlap */
2043                          if (start > n->end || end < n->start)
2044                                  continue;
...
2052                          if (start > n->start)
2053                                  ret = vfio_iommu_iova_insert(&n->list, n->start,
2054                                                               start - 1);
2055                          if (!ret && end < n->end)
2056                                  ret = vfio_iommu_iova_insert(&n->list, end + 1,
2057                                                               n->end);