linux-kernel - Re: [PATCH] iommu: Fix group refcount in iommu_alloc_default

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Message-ID: <20200525130253.GH5075@suse.de>
Date:   Mon, 25 May 2020 15:02:53 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Evan Green <evgreen@...omium.org>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH] iommu: Fix group refcount in iommu_alloc_default_domain()

Hi,

On Fri, May 22, 2020 at 06:31:45PM +0530, Sai Prakash Ranjan wrote:
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index a4c2f122eb8b..05f7b77c432f 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -1491,6 +1491,7 @@ static int iommu_alloc_default_domain(struct device *dev)
>  {
>  	struct iommu_group *group;
>  	unsigned int type;
> +	int ret;
>  
>  	group = iommu_group_get(dev);
>  	if (!group)
> @@ -1501,7 +1502,11 @@ static int iommu_alloc_default_domain(struct device *dev)
>  
>  	type = iommu_get_def_domain_type(dev);
>  
> -	return iommu_group_alloc_default_domain(dev->bus, group, type);
> +	ret = iommu_group_alloc_default_domain(dev->bus, group, type);
> +
> +	iommu_group_put(group);
> +
> +	return ret;
>  }
>  
>  /**

Thanks for the report and the fix. I think it is better to fix this by
not taking a group reference in iommu_alloc_default_domain() at all and
pass group as a parameter. Please see the patch I just sent out.

Regards,

	Joerg