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

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Message-ID: <1f9088b5-b52a-3fa0-2bb1-90ee83294d46@arm.com>
Date:   Mon, 18 Sep 2023 11:08:34 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Baolu Lu <baolu.lu@...ux.intel.com>, joro@...tes.org,
        will@...nel.org
Cc:     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 2023-09-18 06:49, Baolu Lu wrote:
> 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()?

Oh, probably - I don't think I've really noticed that we've grown yet 
another attach interface since I started this. Looks like current users 
are passing appropriate domains by construction, but I concur that that 
path wants covering as well for completeness.

Thanks,
Robin.

> 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