linux-kernel - Re: [PATCH v2 10/12] iommu: Make iommu_queue

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Message-ID: <ZNU1Zev6j92IJRjn@ziepe.ca>
Date:   Thu, 10 Aug 2023 16:07:17 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Kevin Tian <kevin.tian@...el.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Nicolin Chen <nicolinc@...dia.com>,
        Yi Liu <yi.l.liu@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux.dev, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 10/12] iommu: Make iommu_queue_iopf() more generic

On Thu, Jul 27, 2023 at 01:48:35PM +0800, Lu Baolu wrote:
> @@ -137,6 +136,16 @@ int iommu_queue_iopf(struct iommu_fault *fault, struct device *dev)
>  		return 0;
>  	}
>  
> +	if (fault->prm.flags & IOMMU_FAULT_PAGE_REQUEST_PASID_VALID)
> +		domain = iommu_get_domain_for_dev_pasid(dev, fault->prm.pasid, 0);
> +	else
> +		domain = iommu_get_domain_for_dev(dev);

How does the lifetime work for this? What prevents UAF on domain?

> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index ab42cfdd7636..668f4c2bcf65 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -157,7 +157,7 @@ EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
>  /*
>   * I/O page fault handler for SVA
>   */
> -enum iommu_page_response_code
> +static enum iommu_page_response_code
>  iommu_sva_handle_iopf(struct iommu_fault *fault, void *data)
>  {
>  	vm_fault_t ret;
> @@ -241,23 +241,16 @@ static void iopf_handler(struct work_struct *work)
>  {
>  	struct iopf_fault *iopf;
>  	struct iopf_group *group;
> -	struct iommu_domain *domain;
>  	enum iommu_page_response_code status = IOMMU_PAGE_RESP_SUCCESS;
>  
>  	group = container_of(work, struct iopf_group, work);
> -	domain = iommu_get_domain_for_dev_pasid(group->dev,
> -				group->last_fault.fault.prm.pasid, 0);
> -	if (!domain || !domain->iopf_handler)
> -		status = IOMMU_PAGE_RESP_INVALID;
> -
>  	list_for_each_entry(iopf, &group->faults, list) {
>  		/*
>  		 * For the moment, errors are sticky: don't handle subsequent
>  		 * faults in the group if there is an error.
>  		 */
>  		if (status == IOMMU_PAGE_RESP_SUCCESS)
> -			status = domain->iopf_handler(&iopf->fault,
> -						      domain->fault_data);
> +			status = iommu_sva_handle_iopf(&iopf->fault, group->data);
>  	}
>  
>  	iopf_complete_group(group->dev, &group->last_fault, status);
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 157a28a49473..535a36e3edc9 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -3330,7 +3330,7 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
>  	domain->type = IOMMU_DOMAIN_SVA;
>  	mmgrab(mm);
>  	domain->mm = mm;
> -	domain->iopf_handler = iommu_sva_handle_iopf;
> +	domain->iopf_handler = iommu_sva_handle_iopf_group;
>  	domain->fault_data = mm;

This also has lifetime problems on the mm.

The domain should flow into the iommu_sva_handle_iopf() instead of the
void *data.

The SVA code can then just use domain->mm directly.

We need to document/figure out some how to ensure that the faults are
all done processing before a fault enabled domain can be freed.

This patch would be better ordered before the prior patch.

Jason