linux-kernel - Re: [PATCH] iommu/dma: Fix domain init

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Message-ID: <02ebbb90-84bc-4d8c-a7aa-94cd78e0a2a5@arm.com>
Date: Tue, 21 May 2024 16:14:50 +0100
From: Robin Murphy <robin.murphy@....com>
To: Jerry Snitselaar <jsnitsel@...hat.com>
Cc: joro@...tes.org, iommu@...ts.linux.dev, will@...nel.org,
 linux-kernel@...r.kernel.org, Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH] iommu/dma: Fix domain init

On 21/05/2024 5:45 am, Jerry Snitselaar wrote:
> On Mon, May 20, 2024 at 08:14:44PM GMT, Robin Murphy wrote:
>> Despite carefully rewording the kerneldoc to describe the new direct
>> interaction with dma_range_map, it seems I managed to confuse myself in
>> removing the redundant force_aperture check and ended up making the code
>> not do that at all. This led to dma_range_maps inadvertently being able
>> to set iovad->start_pfn = 0, and all the nonsensical chaos which ensues
>> from there. Restore the correct behaviour of constraining base_pfn to
>> the domain aperture regardless of dma_range_map, and not trying to apply
>> dma_range_map constraints to the basic IOVA domain since they will be
>> properly handled with reserved regions later.
>>
>> Reported-by: Jon Hunter <jonathanh@...dia.com>
>> Reported-by: Jerry Snitselaar <jsnitsel@...hat.com>
>> Fixes: e28a114243d1 ("iommu/dma: Make limit checks self-contained")
> 
> I'm seeing this upstream as ad4750b07d34 ("iommu/dma: Make limit checks self-contained") now.

What, you mean when Linus pulls some patches I wrote he *doesn't* also 
rebase my local development branch for me? /facepalm

Joerg, please shout if you'd like a resend for that.

>> Signed-off-by: Robin Murphy <robin.murphy@....com>
>> ---
> 
> Tested-by: Jerry Snitselaar <jsnitsel@...hat.com>
> Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>

Thanks!
Robin.

>>   drivers/iommu/dma-iommu.c | 8 ++++----
>>   1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index 89a53c2f2cf9..1ec89ca75c59 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -685,15 +685,15 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, struct device *dev
>>   
>>   	/* Check the domain allows at least some access to the device... */
>>   	if (map) {
>> -		dma_addr_t base = dma_range_map_min(map);
>> -		if (base > domain->geometry.aperture_end ||
>> +		if (dma_range_map_min(map) > domain->geometry.aperture_end ||
>>   		    dma_range_map_max(map) < domain->geometry.aperture_start) {
>>   			pr_warn("specified DMA range outside IOMMU capability\n");
>>   			return -EFAULT;
>>   		}
>> -		/* ...then finally give it a kicking to make sure it fits */
>> -		base_pfn = max(base, domain->geometry.aperture_start) >> order;
>>   	}
>> +	/* ...then finally give it a kicking to make sure it fits */
>> +	base_pfn = max_t(unsigned long, base_pfn,
>> +			 domain->geometry.aperture_start >> order);
>>   
>>   	/* start_pfn is always nonzero for an already-initialised domain */
>>   	mutex_lock(&cookie->mutex);
>> -- 
>> 2.39.2.101.g768bb238c484.dirty
>>
>