[PATCH] drm/tinydrm: Fix memroy leak in hx8357d_probe

[PATCH] drm/tinydrm: Fix memroy leak in hx8357d_probe

[Navid Emamdoost]

In the implementation of hx8357d_probe() the allocated memory for dbidev
is leaked when an error happens. Release dbidev if any of the  following
calls fail: devm_gpiod_get(), devm_of_find_backlight(),
mipi_dbi_spi_init(), mipi_dbi_init(), drm_dev_register().

Fixes: f300c86e33a6 ("drm: Add an hx8367d tinydrm driver.")
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
---
 drivers/gpu/drm/tiny/hx8357d.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/tiny/hx8357d.c b/drivers/gpu/drm/tiny/hx8357d.c
index 9af8ff84974f..da5ec944f47e 100644
--- a/drivers/gpu/drm/tiny/hx8357d.c
+++ b/drivers/gpu/drm/tiny/hx8357d.c
@@ -232,44 +232,49 @@ static int hx8357d_probe(struct spi_device *spi)
 
 	drm = &dbidev->drm;
 	ret = devm_drm_dev_init(dev, drm, &hx8357d_driver);
-	if (ret) {
-		kfree(dbidev);
-		return ret;
-	}
+	if (ret)
+		goto free_dbidev;
 
 	drm_mode_config_init(drm);
 
 	dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);
 	if (IS_ERR(dc)) {
 		DRM_DEV_ERROR(dev, "Failed to get gpio 'dc'\n");
-		return PTR_ERR(dc);
+		ret = PTR_ERR(dc);
+		goto free_dbidev;
 	}
 
 	dbidev->backlight = devm_of_find_backlight(dev);
-	if (IS_ERR(dbidev->backlight))
-		return PTR_ERR(dbidev->backlight);
+	if (IS_ERR(dbidev->backlight)) {
+		ret = PTR_ERR(dbidev->backlight);
+		goto free_dbidev;
+	}
 
 	device_property_read_u32(dev, "rotation", &rotation);
 
 	ret = mipi_dbi_spi_init(spi, &dbidev->dbi, dc);
 	if (ret)
-		return ret;
+		goto free_dbidev;
 
 	ret = mipi_dbi_dev_init(dbidev, &hx8357d_pipe_funcs, &yx350hv15_mode, rotation);
 	if (ret)
-		return ret;
+		goto free_dbidev;
 
 	drm_mode_config_reset(drm);
 
 	ret = drm_dev_register(drm, 0);
 	if (ret)
-		return ret;
+		goto free_dbidev;
 
 	spi_set_drvdata(spi, drm);
 
 	drm_fbdev_generic_setup(drm, 0);
 
 	return 0;
+
+free_dbidev:
+	kfree(dbidev);
+	return ret;
 }
 
 static int hx8357d_remove(struct spi_device *spi)
-- 
2.17.1

Re: [PATCH] drm/tinydrm: Fix memroy leak in hx8357d_probe

[Markus Elfring]

…
> +++ b/drivers/gpu/drm/tiny/hx8357d.c
> @@ -232,44 +232,49 @@ static int hx8357d_probe(struct spi_device *spi)
…
> +		goto free_dbidev;
>
>  	spi_set_drvdata(spi, drm);

I got another development concern here.
Can it make sense to pass the variable “dbidev” instead of “drm”?


…
> +free_dbidev:
> +	kfree(dbidev);
…

I became curious if there is a need for such a memory release at another place.
How do you think about to add this function call also to the implementation
of the function “hx8357d_remove”?

Regards,
Markus

Re: drm/tinydrm: Fix memory leak in hx8357d_probe

[Markus Elfring]

> …
>> +free_dbidev:
>> +	kfree(dbidev);
> …
>
> I became curious if there is a need for such a memory release at another place.

I have taken another look also at a related implementation detail.
Now I have realised that the desired clean-up should usually be achieved by
the callback function “mipi_dbi_release” for this software module.
https://elixir.bootlin.com/linux/v5.4-rc2/source/drivers/gpu/drm/drm_mipi_dbi.c#L581
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpu/drm/drm_mipi_dbi.c?id=0365fb6baeb1ebefbbdad9e3f48bab9b3ccb8df3#n581

Regards,
Markus

Re: [PATCH] drm/tinydrm: Fix memory leak in hx8357d_probe()

[Markus Elfring]

Please avoid also another typo in the (previous) patch subject.

Regards,
Markus

Re: [PATCH] drm/tinydrm: Fix memroy leak in hx8357d_probe

[Noralf Trønnes]

Hi Navid,

Den 27.10.2019 18.32, skrev Navid Emamdoost:
> In the implementation of hx8357d_probe() the allocated memory for dbidev
> is leaked when an error happens. Release dbidev if any of the  following
> calls fail: devm_gpiod_get(), devm_of_find_backlight(),
> mipi_dbi_spi_init(), mipi_dbi_init(), drm_dev_register().
> 
> Fixes: f300c86e33a6 ("drm: Add an hx8367d tinydrm driver.")
> Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
> ---
>  drivers/gpu/drm/tiny/hx8357d.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/gpu/drm/tiny/hx8357d.c b/drivers/gpu/drm/tiny/hx8357d.c
> index 9af8ff84974f..da5ec944f47e 100644
> --- a/drivers/gpu/drm/tiny/hx8357d.c
> +++ b/drivers/gpu/drm/tiny/hx8357d.c
> @@ -232,44 +232,49 @@ static int hx8357d_probe(struct spi_device *spi)
>  
>  	drm = &dbidev->drm;
>  	ret = devm_drm_dev_init(dev, drm, &hx8357d_driver);

This is a device managed function that releases its resource(s) on
device:driver unbind like the other devm_ functions (it can't free
dbidev if it fails hence the kfree in the error path here).

This is the release call path:

devm_drm_dev_init_release -> drm_dev_put -> drm_dev_release ->
dev->driver->release : mipi_dbi_release.

Noralf.

> -	if (ret) {
> -		kfree(dbidev);
> -		return ret;
> -	}
> +	if (ret)
> +		goto free_dbidev;
>  
>  	drm_mode_config_init(drm);
>  
>  	dc = devm_gpiod_get(dev, "dc", GPIOD_OUT_LOW);
>  	if (IS_ERR(dc)) {
>  		DRM_DEV_ERROR(dev, "Failed to get gpio 'dc'\n");
> -		return PTR_ERR(dc);
> +		ret = PTR_ERR(dc);
> +		goto free_dbidev;
>  	}
>  
>  	dbidev->backlight = devm_of_find_backlight(dev);
> -	if (IS_ERR(dbidev->backlight))
> -		return PTR_ERR(dbidev->backlight);
> +	if (IS_ERR(dbidev->backlight)) {
> +		ret = PTR_ERR(dbidev->backlight);
> +		goto free_dbidev;
> +	}
>  
>  	device_property_read_u32(dev, "rotation", &rotation);
>  
>  	ret = mipi_dbi_spi_init(spi, &dbidev->dbi, dc);
>  	if (ret)
> -		return ret;
> +		goto free_dbidev;
>  
>  	ret = mipi_dbi_dev_init(dbidev, &hx8357d_pipe_funcs, &yx350hv15_mode, rotation);
>  	if (ret)
> -		return ret;
> +		goto free_dbidev;
>  
>  	drm_mode_config_reset(drm);
>  
>  	ret = drm_dev_register(drm, 0);
>  	if (ret)
> -		return ret;
> +		goto free_dbidev;
>  
>  	spi_set_drvdata(spi, drm);
>  
>  	drm_fbdev_generic_setup(drm, 0);
>  
>  	return 0;
> +
> +free_dbidev:
> +	kfree(dbidev);
> +	return ret;
>  }
>  
>  static int hx8357d_remove(struct spi_device *spi)
>