linux-kernel - Re: [PATCH v8 1/5] iommu/arm-smmu: Destroy domain context in failure path

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Date:   Wed, 7 Mar 2018 12:20:45 +0000
From:   Robin Murphy <robin.murphy@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>, joro@...tes.org,
        robh+dt@...nel.org, mark.rutland@....com, rjw@...ysocki.net,
        will.deacon@....com, robdclark@...il.com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     tfiga@...omium.org, jcrouse@...eaurora.org, sboyd@...eaurora.org,
        sricharan@...eaurora.org, m.szyprowski@...sung.com,
        architt@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v8 1/5] iommu/arm-smmu: Destroy domain context in failure
 path

On 02/03/18 10:10, Vivek Gautam wrote:
> If we fail after initializing domain_context, we should destroy
> the context to free up resources.

Have another think about why the "problem" this patch caters for cannot 
ever happen (hint: consider how domain->smmu is used in 
arm_smmu_init_domain_context()). And then also about the really 
catastrophically bad problem it actually introduces (hint: 
"iommu_attach(domain, good_dev); iommu_attach(domain, bad_dev);")

Robin.

> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> ---
> 
>   * New patch added in this series.
> 
>   drivers/iommu/arm-smmu.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 69e7c60792a8..ffc152c36002 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -1223,11 +1223,16 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
>   		dev_err(dev,
>   			"cannot attach to SMMU %s whilst already attached to domain on SMMU %s\n",
>   			dev_name(smmu_domain->smmu->dev), dev_name(smmu->dev));
> -		return -EINVAL;
> +		ret = -EINVAL;
> +		goto destroy_domain;
>   	}
>   
>   	/* Looks ok, so add the device to the domain */
>   	return arm_smmu_domain_add_master(smmu_domain, fwspec);
> +
> +destroy_domain:
> +	arm_smmu_destroy_domain_context(domain);
> +	return ret;
>   }
>   
>   static int arm_smmu_map(struct iommu_domain *domain, unsigned long iova,
>