Re: [PATCH V1] iommu/sva: Fix crash in iommu_sva_unbind_device()

[Lizhi Hou]

On 2/28/26 04:14, Yi Liu wrote:
> On 2/26/26 06:09, Lizhi Hou wrote:
> > > > diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> > > > index 07d64908a05f..523b8c65c86f 100644
> > > > --- a/drivers/iommu/iommu-sva.c
> > > > +++ b/drivers/iommu/iommu-sva.c
> > > > @@ -179,6 +179,7 @@ void iommu_sva_unbind_device(struct iommu_sva
> > > > *handle)
> > > >               return;
> > > >       }
> > > >
> > > > +     mmgrab(domain->mm);
> > > >       iommu_detach_device_pasid(domain, dev, iommu_mm->pasid);
> > > >       if (--domain->users == 0) {
> > > >               list_del(&domain->next);
> > > > @@ -190,6 +191,7 @@ void iommu_sva_unbind_device(struct iommu_sva
> > > > *handle)
> > > >               if (list_empty(&iommu_sva_mms))
> > > >                       iommu_sva_present = false;
> > > >       }
> > > > +     mmdrop(domain->mm);
> > > >
> > > >       mutex_unlock(&iommu_sva_lock);
> > > >       kfree(handle);
> > >
> > > will moving the below hunk in front of iommu_domain_free() simpler?
> > > Only when (--domain->users == 0), shall the code check if sva_domains
> > > is empty. right?
> >
> > I am not sure if this can be moved in front of iommu_domain_free(). Will
> > iommu_domain_free() be possible to impact sva_domains?
>
> sva_domains is used to track domains associated with the same mm in the
> generic layer. iommu_domain_free() calls vendor iommu driver's free() op
> with domain type specific operations. I don't think it should impact the
> sva_domains.
>
> > iommu_domain_free() calls domain->ops->free(). Could this call back free
> > sva_domain?
>
> I think so. Check intel_mm_free_notifier() as an example.

So if this is true, after calling iommu_domain_free(), the following 
check list_empty(&iommu_mm->sva_domains) could become to true because of 
domain free. If we move the check in front (before iommu_domain_free()), 
the check could be false. That seems leading incorrect iommu_sva_present

Lizhi

> Regards,
> Yi Liu