linux-kernel - Re: [PATCH] iommu/tegra-smmu: Fix missing put_device() call in tegra_smmu

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Message-ID: <Yg0AqkLA7eXQOuh2@orome>
Date:   Wed, 16 Feb 2022 14:48:26 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Miaoqian Lin <linmq006@...il.com>
Cc:     Krishna Reddy <vdumpa@...dia.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Nicolin Chen <nicoleotsuka@...il.com>,
        linux-tegra@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/tegra-smmu: Fix missing put_device() call in
 tegra_smmu_find

On Fri, Jan 07, 2022 at 08:09:11AM +0000, Miaoqian Lin wrote:
> The reference taken by 'of_find_device_by_node()' must be released when
> not needed anymore.
> Add the corresponding 'put_device()' in the error handling path.
> 
> Fixes: 765a9d1d02b2 ("iommu/tegra-smmu: Fix mc errors on tegra124-nyan")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
>  drivers/iommu/tegra-smmu.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/tegra-smmu.c b/drivers/iommu/tegra-smmu.c
> index e900e3c46903..2561ce8a2ce8 100644
> --- a/drivers/iommu/tegra-smmu.c
> +++ b/drivers/iommu/tegra-smmu.c
> @@ -808,8 +808,10 @@ static struct tegra_smmu *tegra_smmu_find(struct device_node *np)
>  		return NULL;
>  
>  	mc = platform_get_drvdata(pdev);
> -	if (!mc)
> +	if (!mc) {
> +		put_device(&pdev->dev);
>  		return NULL;
> +	}
>  
>  	return mc->smmu;
>  }

Sorry for the late reply, looks correct. We probably also need a similar
call in ->release_device(). I also wonder if we should be returning an
-EPROBE_DEFER here, which is technically the correct thing to do, though
in practice that will likely never happen because these pointers are set
during an arch_initcall, so should always be available by the time a
driver tries to attach to an IOMMU.

Acked-by: Thierry Reding <treding@...dia.com>

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