linux-kernel - Re: [PATCH v3 3/7] iommu: Validate that devices match domains

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Message-ID: <a39dcdcb-e904-a09d-f553-66bac5257205@linux.intel.com>
Date:   Mon, 18 Sep 2023 13:49:42 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Robin Murphy <robin.murphy@....com>, joro@...tes.org,
        will@...nel.org
Cc:     baolu.lu@...ux.intel.com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        jgg@...dia.com
Subject: Re: [PATCH v3 3/7] iommu: Validate that devices match domains

On 9/16/23 12:58 AM, Robin Murphy wrote:
> Before we can allow drivers to coexist, we need to make sure that one
> driver's domain ops can't misinterpret another driver's dev_iommu_priv
> data. To that end, add a token to the domain so we can remember how it
> was allocated - for now this may as well be the device ops, since they
> still correlate 1:1 with drivers. We can trust ourselves for internal
> default domain attachment, so add the check where it covers both the
> external attach interfaces.
> 
> Reviewed-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jason Gunthorpe <jgg@...dia.com>
> Signed-off-by: Robin Murphy <robin.murphy@....com>
> ---
>   drivers/iommu/iommu.c | 13 +++++++++----
>   include/linux/iommu.h |  1 +
>   2 files changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 2f29ee9dea64..f4cc91227b22 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2000,26 +2000,28 @@ EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
>   static struct iommu_domain *__iommu_domain_alloc(const struct bus_type *bus,
>   						 unsigned type)
>   {
> +	const struct iommu_ops *ops = bus ? bus->iommu_ops : NULL;
>   	struct iommu_domain *domain;
>   	unsigned int alloc_type = type & IOMMU_DOMAIN_ALLOC_FLAGS;
>   
> -	if (bus == NULL || bus->iommu_ops == NULL)
> +	if (!ops)
>   		return NULL;
>   
> -	domain = bus->iommu_ops->domain_alloc(alloc_type);
> +	domain = ops->domain_alloc(alloc_type);
>   	if (!domain)
>   		return NULL;
>   
>   	domain->type = type;
> +	domain->owner = ops;
>   	/*
>   	 * If not already set, assume all sizes by default; the driver
>   	 * may override this later
>   	 */
>   	if (!domain->pgsize_bitmap)
> -		domain->pgsize_bitmap = bus->iommu_ops->pgsize_bitmap;
> +		domain->pgsize_bitmap = ops->pgsize_bitmap;
>   
>   	if (!domain->ops)
> -		domain->ops = bus->iommu_ops->default_domain_ops;
> +		domain->ops = ops->default_domain_ops;
>   
>   	if (iommu_is_dma_domain(domain) && iommu_get_dma_cookie(domain)) {
>   		iommu_domain_free(domain);
> @@ -2176,6 +2178,9 @@ static int __iommu_attach_group(struct iommu_domain *domain,
>   	    group->domain != group->blocking_domain)
>   		return -EBUSY;
>   
> +	if (dev_iommu_ops(iommu_group_first_dev(group)) != domain->owner)
> +		return -EINVAL;

Should we apply this check in iommu_attach_device_pasid()?

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3bfc56df4f78..43acf1b8ed56 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3414,6 +3414,9 @@ int iommu_attach_device_pasid(struct iommu_domain 
*domain,
         if (!group)
                 return -ENODEV;

+       if (dev_iommu_ops(dev) != domain->owner)
+               return -EINVAL;
+
         mutex_lock(&group->mutex);
         curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain, 
GFP_KERNEL);
         if (curr) {

> +
>   	return __iommu_group_set_domain(group, domain);
>   }
>   
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index a249e10c8e9f..75ffcac199e3 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -95,6 +95,7 @@ struct iommu_domain_geometry {
>   struct iommu_domain {
>   	unsigned type;
>   	const struct iommu_domain_ops *ops;
> +	const struct iommu_ops *owner; /* Whose domain_alloc we came from */
>   	unsigned long pgsize_bitmap;	/* Bitmap of page sizes in use */
>   	struct iommu_domain_geometry geometry;
>   	struct iommu_dma_cookie *iova_cookie;

Best regards,
baolu