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

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Message-ID: <20251009011535.GB3833649@ziepe.ca>
Date: Wed, 8 Oct 2025 22:15:35 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Alex Mastro <amastro@...com>
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 03:19:07PM -0700, Alex Mastro wrote:
> 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?

IDK, if it is actually internally consistent and not using end
interchangably then it is probably Ok to keep doing it. If it is
already inconsistent then use last for new code and leave the old as
is?

Jason