[PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

[PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

[Gustavo A. R. Silva]

Check return value from call to of_match_device()
in order to prevent a NULL pointer dereference.

In case of NULL print error message and return -ENODEV

Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index adaaafc..6a77dea 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
 	int i;
 
 	match = of_match_device(of_mtk_match, &pdev->dev);
+	if (!match) {
+		dev_err(&pdev->dev, "failed to match device\n");
+		return -ENODEV;
+	}
+
 	soc = (struct mtk_soc_data *)match->data;
 
 	eth = devm_kzalloc(&pdev->dev, sizeof(*eth), GFP_KERNEL);
-- 
2.5.0

Re: [PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

[Matthias Brugger]

On 07/07/2017 09:11 AM, Gustavo A. R. Silva wrote:
> Check return value from call to of_match_device()
> in order to prevent a NULL pointer dereference.
> 
> In case of NULL print error message and return -ENODEV
> 
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
> ---

Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>

>   drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
>   1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index adaaafc..6a77dea 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
>   	int i;
>   
>   	match = of_match_device(of_mtk_match, &pdev->dev);
> +	if (!match) {
> +		dev_err(&pdev->dev, "failed to match device\n");
> +		return -ENODEV;
> +	}
> +
>   	soc = (struct mtk_soc_data *)match->data;
>   
>   	eth = devm_kzalloc(&pdev->dev, sizeof(*eth), GFP_KERNEL);
> 

Re: [PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

[Andrew Lunn]

On Fri, Jul 07, 2017 at 02:11:35AM -0500, Gustavo A. R. Silva wrote:
> Check return value from call to of_match_device()
> in order to prevent a NULL pointer dereference.
> 
> In case of NULL print error message and return -ENODEV
> 
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index adaaafc..6a77dea 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
>  	int i;
>  
>  	match = of_match_device(of_mtk_match, &pdev->dev);
> +	if (!match) {
> +		dev_err(&pdev->dev, "failed to match device\n");
> +		return -ENODEV;
> +	}
> +
>  	soc = (struct mtk_soc_data *)match->data;

Hi Gustavo

I think you are fixing the wrong thing. The soc variable is unused. Also,

const struct of_device_id of_mtk_match[] = {
        { .compatible = "mediatek,mt2701-eth" },
        {},
};

So match->data is NULL. This code is all pointless and should be
removed, rather than try to avoid a NULL pointer dereference which can
not actually happen.

	Andrew

Re: [PATCH] net: ethernet: mediatek: add NULL check on of_match_device() return value

[Gustavo A. R. Silva]

Hi Andrew,

Quoting Andrew Lunn <andrew@lunn.ch>:

> On Fri, Jul 07, 2017 at 02:11:35AM -0500, Gustavo A. R. Silva wrote:
>> Check return value from call to of_match_device()
>> in order to prevent a NULL pointer dereference.
>>
>> In case of NULL print error message and return -ENODEV
>>
>> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
>> ---
>>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c  
>> b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> index adaaafc..6a77dea 100644
>> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
>> @@ -2408,6 +2408,11 @@ static int mtk_probe(struct platform_device *pdev)
>>  	int i;
>>
>>  	match = of_match_device(of_mtk_match, &pdev->dev);
>> +	if (!match) {
>> +		dev_err(&pdev->dev, "failed to match device\n");
>> +		return -ENODEV;
>> +	}
>> +
>>  	soc = (struct mtk_soc_data *)match->data;
>
> Hi Gustavo
>
> I think you are fixing the wrong thing. The soc variable is unused. Also,
>
> const struct of_device_id of_mtk_match[] = {
>         { .compatible = "mediatek,mt2701-eth" },
>         {},
> };
>
> So match->data is NULL. This code is all pointless and should be
> removed, rather than try to avoid a NULL pointer dereference which can
> not actually happen.
>

You are right. Thank you for pointing it out. I'll remove that code  
and send a new patch shortly.

Thanks!
--
Gustavo A. R. Silva

[PATCH] net: ethernet: mediatek: remove useless code in mtk_probe()

[Gustavo A. R. Silva]

Remove useless local variables _match_, _soc_ and the code related.

Notice that

const struct of_device_id of_mtk_match[] = {
        { .compatible = "mediatek,mt2701-eth" },
        {},
};

So match->data is NULL.

Suggested-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index adaaafc..b9a5a65 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -2401,15 +2401,10 @@ static int mtk_probe(struct platform_device *pdev)
 {
 	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	struct device_node *mac_np;
-	const struct of_device_id *match;
-	struct mtk_soc_data *soc;
 	struct mtk_eth *eth;
 	int err;
 	int i;
 
-	match = of_match_device(of_mtk_match, &pdev->dev);
-	soc = (struct mtk_soc_data *)match->data;
-
 	eth = devm_kzalloc(&pdev->dev, sizeof(*eth), GFP_KERNEL);
 	if (!eth)
 		return -ENOMEM;
-- 
2.5.0

Re: [PATCH] net: ethernet: mediatek: remove useless code in mtk_probe()

[Sean Wang]

Hi,  Gustavo

It indeed is useless at the current time point.


but actually I will add new SoC support to the driver in the next week,
which requires the variable match :-(

	Sean


On Fri, 2017-07-07 at 15:23 -0500, Gustavo A. R. Silva wrote:
> Remove useless local variables _match_, _soc_ and the code related.
> 
> Notice that
> 
> const struct of_device_id of_mtk_match[] = {
>         { .compatible = "mediatek,mt2701-eth" },
>         {},
> };
> 
> So match->data is NULL.
> 
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>
> ---
>  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 5 -----
>  1 file changed, 5 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> index adaaafc..b9a5a65 100644
> --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> @@ -2401,15 +2401,10 @@ static int mtk_probe(struct platform_device *pdev)
>  {
>  	struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
>  	struct device_node *mac_np;
> -	const struct of_device_id *match;
> -	struct mtk_soc_data *soc;
>  	struct mtk_eth *eth;
>  	int err;
>  	int i;
>  
> -	match = of_match_device(of_mtk_match, &pdev->dev);
> -	soc = (struct mtk_soc_data *)match->data;
> -
>  	eth = devm_kzalloc(&pdev->dev, sizeof(*eth), GFP_KERNEL);
>  	if (!eth)
>  		return -ENOMEM;

Re: [PATCH] net: ethernet: mediatek: remove useless code in mtk_probe()

[David Miller]

From: "Gustavo A. R. Silva" <garsilva@embeddedor.com>
Date: Fri, 7 Jul 2017 15:23:34 -0500

> Remove useless local variables _match_, _soc_ and the code related.
> 
> Notice that
> 
> const struct of_device_id of_mtk_match[] = {
>         { .compatible = "mediatek,mt2701-eth" },
>         {},
> };
> 
> So match->data is NULL.
> 
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Gustavo A. R. Silva <garsilva@embeddedor.com>

Applied, thanks.

If someone needs this they can it back, in a less buggy form.