linux-kernel - Re: [PATCH v2] drm/tegra: dc: rgb: Fix refcount leak in tegra_dc_rgb

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Message-ID: <c1ccad8a-8063-1156-f18f-8cc13c65a11b@collabora.com>
Date:   Fri, 3 Jun 2022 16:58:56 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Miaoqian Lin <linmq006@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Zhang <markz@...dia.com>,
        Terje Bergstrom <tbergstrom@...dia.com>,
        Dave Airlie <airlied@...hat.com>,
        dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] drm/tegra: dc: rgb: Fix refcount leak in
 tegra_dc_rgb_probe

On 6/3/22 16:27, Miaoqian Lin wrote:
> of_get_child_by_name() returns a node pointer with refcount
> incremented, we should use of_node_put() on it when not need anymore.
> So add of_node_put() in error paths.
> 
> Fixes: d8f4a9eda006 ("drm: Add NVIDIA Tegra20 support")
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---
> changes in v2:
> - update Fixes tag.
> v1 Link: https://lore.kernel.org/r/20220602155615.43277-1-linmq006@gmail.com
> ---
>  drivers/gpu/drm/tegra/rgb.c | 31 +++++++++++++++++++++----------
>  1 file changed, 21 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tegra/rgb.c b/drivers/gpu/drm/tegra/rgb.c
> index ff8fce36d2aa..cef2b1b72385 100644
> --- a/drivers/gpu/drm/tegra/rgb.c
> +++ b/drivers/gpu/drm/tegra/rgb.c
> @@ -196,12 +196,16 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
>  	int err;
>  
>  	np = of_get_child_by_name(dc->dev->of_node, "rgb");
> -	if (!np || !of_device_is_available(np))
> -		return -ENODEV;
> +	if (!np || !of_device_is_available(np)) {
> +		err = -ENODEV;
> +		goto err_put_node;
> +	}
>  
>  	rgb = devm_kzalloc(dc->dev, sizeof(*rgb), GFP_KERNEL);
> -	if (!rgb)
> -		return -ENOMEM;
> +	if (!rgb) {
> +		err = -ENOMEM;
> +		goto err_put_node;
> +	}
>  
>  	rgb->output.dev = dc->dev;
>  	rgb->output.of_node = np;
> @@ -209,31 +213,34 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
>  
>  	err = tegra_output_probe(&rgb->output);
>  	if (err < 0)
> -		return err;
> +		goto err_put_node;
> +
>  
>  	rgb->clk = devm_clk_get(dc->dev, NULL);
>  	if (IS_ERR(rgb->clk)) {
>  		dev_err(dc->dev, "failed to get clock\n");
> -		return PTR_ERR(rgb->clk);
> +		err =  PTR_ERR(rgb->clk);
> +		goto err_put_node;
>  	}
>  
>  	rgb->clk_parent = devm_clk_get(dc->dev, "parent");
>  	if (IS_ERR(rgb->clk_parent)) {
>  		dev_err(dc->dev, "failed to get parent clock\n");
> -		return PTR_ERR(rgb->clk_parent);
> +		err = PTR_ERR(rgb->clk_parent);
> +		goto err_put_node;
>  	}
>  
>  	err = clk_set_parent(rgb->clk, rgb->clk_parent);
>  	if (err < 0) {
>  		dev_err(dc->dev, "failed to set parent clock: %d\n", err);
> -		return err;
> +		goto err_put_node;
>  	}
>  
>  	rgb->pll_d_out0 = clk_get_sys(NULL, "pll_d_out0");
>  	if (IS_ERR(rgb->pll_d_out0)) {
>  		err = PTR_ERR(rgb->pll_d_out0);
>  		dev_err(dc->dev, "failed to get pll_d_out0: %d\n", err);
> -		return err;
> +		goto err_put_node;
>  	}
>  
>  	if (dc->soc->has_pll_d2_out0) {
> @@ -241,13 +248,17 @@ int tegra_dc_rgb_probe(struct tegra_dc *dc)
>  		if (IS_ERR(rgb->pll_d2_out0)) {
>  			err = PTR_ERR(rgb->pll_d2_out0);
>  			dev_err(dc->dev, "failed to get pll_d2_out0: %d\n", err);
> -			return err;
> +			goto err_put_node;
>  		}
>  	}
>  
>  	dc->rgb = &rgb->output;
>  
>  	return 0;
> +
> +err_put_node:
> +	of_node_put(np);
> +	return err;
>  }
>  
>  int tegra_dc_rgb_remove(struct tegra_dc *dc)

Doesn't look like the node is put on driver removal either. Hence you
should make it resource-managed.

-- 
Best regards,
Dmitry