linux-kernel - Re: [PATCH] drm/msm/dsi: Fix some reference counted resource leaks

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Message-ID: <9ea0857b-fca5-3011-6ebb-3ff6173ac037@linaro.org>
Date:   Fri, 1 Oct 2021 18:20:51 +0300
From:   Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        robdclark@...il.com, sean@...rly.run, airlied@...ux.ie,
        daniel@...ll.ch, abhinavk@...eaurora.org, hali@...eaurora.org
Cc:     linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        freedreno@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/msm/dsi: Fix some reference counted resource leaks

On 06/08/2021 12:15, Christophe JAILLET wrote:
> 'of_find_device_by_node()' takes a reference that must be released when
> not needed anymore.
> This is expected to be done in 'dsi_destroy()'.
> 
> However, there are 2 issues in 'dsi_get_phy()'.
> 
> First, if 'of_find_device_by_node()' succeeds but 'platform_get_drvdata()'
> returns NULL, 'msm_dsi->phy_dev' will still be NULL, and the reference
> won't be released in 'dsi_destroy()'.
> 
> Secondly, as 'of_find_device_by_node()' already takes a reference, there is
> no need for an additional 'get_device()'.
> 
> Move the assignment to 'msm_dsi->phy_dev' a few lines above and remove the
> unneeded 'get_device()' to solve both issues.
> 
> Fixes: ec31abf6684e ("drm/msm/dsi: Separate PHY to another platform device")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>

> ---
> Review carefully, management of reference counted resources is sometimes
> tricky.
> ---
>   drivers/gpu/drm/msm/dsi/dsi.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/drm/msm/dsi/dsi.c b/drivers/gpu/drm/msm/dsi/dsi.c
> index 75afc12a7b25..29d11f1cb79b 100644
> --- a/drivers/gpu/drm/msm/dsi/dsi.c
> +++ b/drivers/gpu/drm/msm/dsi/dsi.c
> @@ -26,8 +26,10 @@ static int dsi_get_phy(struct msm_dsi *msm_dsi)
>   	}
>   
>   	phy_pdev = of_find_device_by_node(phy_node);
> -	if (phy_pdev)
> +	if (phy_pdev) {
>   		msm_dsi->phy = platform_get_drvdata(phy_pdev);
> +		msm_dsi->phy_dev = &phy_pdev->dev;
> +	}
>   
>   	of_node_put(phy_node);
>   
> @@ -36,8 +38,6 @@ static int dsi_get_phy(struct msm_dsi *msm_dsi)
>   		return -EPROBE_DEFER;
>   	}
>   
> -	msm_dsi->phy_dev = get_device(&phy_pdev->dev);
> -
>   	return 0;
>   }
>   
> 


-- 
With best wishes
Dmitry