[PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Christophe JAILLET]

If an error occurs, 'mlx4_en_destroy_netdev()' is called.
It then calls 'mlx4_en_free_resources()' which does the needed resources
cleanup.

So, doing some explicit kfree in the error handling path would lead to
some double kfree.

Simplify code to avoid such a case.

Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index e0adac4a9a19..9670b33fc9b1 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -3324,12 +3324,11 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
 					   MAX_TX_RINGS, GFP_KERNEL);
 		if (!priv->tx_ring[t]) {
 			err = -ENOMEM;
-			goto err_free_tx;
+			goto out;
 		}
 		priv->tx_cq[t] = kzalloc(sizeof(struct mlx4_en_cq *) *
 					 MAX_TX_RINGS, GFP_KERNEL);
 		if (!priv->tx_cq[t]) {
-			kfree(priv->tx_ring[t]);
 			err = -ENOMEM;
 			goto out;
 		}
@@ -3582,11 +3581,6 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
 
 	return 0;
 
-err_free_tx:
-	while (t--) {
-		kfree(priv->tx_ring[t]);
-		kfree(priv->tx_cq[t]);
-	}
 out:
 	mlx4_en_destroy_netdev(dev);
 	return err;
-- 
2.17.0

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Yuval Shaia]

On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
> If an error occurs, 'mlx4_en_destroy_netdev()' is called.
> It then calls 'mlx4_en_free_resources()' which does the needed resources
> cleanup.
> 
> So, doing some explicit kfree in the error handling path would lead to
> some double kfree.

Patch make sense but what's bothering me is that mlx4_en_free_resources
loops on the entire array, assuming !priv->tx_ring[t] means entry is
allocated but the existing code does not assume that, see [1]. So i looked
to see where tx_ring array is zeroed and didn't find it.

Am i missing something here.

> 
> Simplify code to avoid such a case.
> 
> Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>  drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index e0adac4a9a19..9670b33fc9b1 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -3324,12 +3324,11 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
>  					   MAX_TX_RINGS, GFP_KERNEL);
>  		if (!priv->tx_ring[t]) {
>  			err = -ENOMEM;
> -			goto err_free_tx;
> +			goto out;
>  		}
>  		priv->tx_cq[t] = kzalloc(sizeof(struct mlx4_en_cq *) *
>  					 MAX_TX_RINGS, GFP_KERNEL);
>  		if (!priv->tx_cq[t]) {
> -			kfree(priv->tx_ring[t]);
>  			err = -ENOMEM;
>  			goto out;
>  		}
> @@ -3582,11 +3581,6 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
>  
>  	return 0;
>  
> -err_free_tx:
> -	while (t--) {

[1]

> -		kfree(priv->tx_ring[t]);
> -		kfree(priv->tx_cq[t]);
> -	}
>  out:
>  	mlx4_en_destroy_netdev(dev);
>  	return err;
> -- 
> 2.17.0
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Dan Carpenter]

On Thu, May 10, 2018 at 04:38:08PM +0300, Yuval Shaia wrote:
> On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
> > If an error occurs, 'mlx4_en_destroy_netdev()' is called.
> > It then calls 'mlx4_en_free_resources()' which does the needed resources
> > cleanup.
> > 
> > So, doing some explicit kfree in the error handling path would lead to
> > some double kfree.
> 
> Patch make sense but what's bothering me is that mlx4_en_free_resources
> loops on the entire array, assuming !priv->tx_ring[t] means entry is
> allocated but the existing code does not assume that, see [1]. So i looked
> to see where tx_ring array is zeroed and didn't find it.
> 
> Am i missing something here.
> 

It's zeroed twice.  alloc_etherdev_mqs() allocates zeroed memory and
then we do a memset(priv, 0, sizeof(struct mlx4_en_priv));

regards,
dan carpenter

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Christophe JAILLET]

Le 10/05/2018 à 15:38, Yuval Shaia a écrit :
> On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
>> If an error occurs, 'mlx4_en_destroy_netdev()' is called.
>> It then calls 'mlx4_en_free_resources()' which does the needed resources
>> cleanup.
>>
>> So, doing some explicit kfree in the error handling path would lead to
>> some double kfree.
> Patch make sense but what's bothering me is that mlx4_en_free_resources
> loops on the entire array, assuming !priv->tx_ring[t] means entry is
> allocated but the existing code does not assume that, see [1]. So i looked
> to see where tx_ring array is zeroed and didn't find it.
>
> Am i missing something here.
My understanding is that the array is zeoed at line 3289, when the whole 
priv struct is memset(0)'ed (also done in alloc_etherdev_mqs but leaving 
an explicit memset help to remind that the struct is zeroed)
If speed matters here (and I don't think so), the memset could be saved 
(the mlx4_en_priv struct is quite big after all), but at least a comment 
should remind that it is initialized within alloc_etherdev_mqs.

CJ


>> Simplify code to avoid such a case.
>>
>> Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
>> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
>> ---
>>   drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 8 +-------
>>   1 file changed, 1 insertion(+), 7 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
>> index e0adac4a9a19..9670b33fc9b1 100644
>> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
>> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
>> @@ -3324,12 +3324,11 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
>>   					   MAX_TX_RINGS, GFP_KERNEL);
>>   		if (!priv->tx_ring[t]) {
>>   			err = -ENOMEM;
>> -			goto err_free_tx;
>> +			goto out;
>>   		}
>>   		priv->tx_cq[t] = kzalloc(sizeof(struct mlx4_en_cq *) *
>>   					 MAX_TX_RINGS, GFP_KERNEL);
>>   		if (!priv->tx_cq[t]) {
>> -			kfree(priv->tx_ring[t]);
>>   			err = -ENOMEM;
>>   			goto out;
>>   		}
>> @@ -3582,11 +3581,6 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
>>   
>>   	return 0;
>>   
>> -err_free_tx:
>> -	while (t--) {
> [1]
>
>> -		kfree(priv->tx_ring[t]);
>> -		kfree(priv->tx_cq[t]);
>> -	}
>>   out:
>>   	mlx4_en_destroy_netdev(dev);
>>   	return err;
>> -- 
>> 2.17.0
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Tariq Toukan]

On 10/05/2018 5:18 PM, Dan Carpenter wrote:
> On Thu, May 10, 2018 at 04:38:08PM +0300, Yuval Shaia wrote:
>> On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
>>> If an error occurs, 'mlx4_en_destroy_netdev()' is called.
>>> It then calls 'mlx4_en_free_resources()' which does the needed resources
>>> cleanup.
>>>
>>> So, doing some explicit kfree in the error handling path would lead to
>>> some double kfree.
>>
>> Patch make sense but what's bothering me is that mlx4_en_free_resources
>> loops on the entire array, assuming !priv->tx_ring[t] means entry is
>> allocated but the existing code does not assume that, see [1]. So i looked
>> to see where tx_ring array is zeroed and didn't find it.
>>
>> Am i missing something here.
>>
> 
> It's zeroed twice.  alloc_etherdev_mqs() allocates zeroed memory and
> then we do a memset(priv, 0, sizeof(struct mlx4_en_priv));
> 
> regards,
> dan carpenter
> 

We do zero (twice) on init, that's right. But I think Yuval's comment is 
valid in case of the driver went into configuration change, or down/up, 
that reallocates the rings. I'm double checking this.

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Tariq Toukan]

On 10/05/2018 5:36 PM, Tariq Toukan wrote:
> 
> 
> On 10/05/2018 5:18 PM, Dan Carpenter wrote:
>> On Thu, May 10, 2018 at 04:38:08PM +0300, Yuval Shaia wrote:
>>> On Thu, May 10, 2018 at 09:02:26AM +0200, Christophe JAILLET wrote:
>>>> If an error occurs, 'mlx4_en_destroy_netdev()' is called.
>>>> It then calls 'mlx4_en_free_resources()' which does the needed 
>>>> resources
>>>> cleanup.
>>>>
>>>> So, doing some explicit kfree in the error handling path would lead to
>>>> some double kfree.
>>>
>>> Patch make sense but what's bothering me is that mlx4_en_free_resources
>>> loops on the entire array, assuming !priv->tx_ring[t] means entry is
>>> allocated but the existing code does not assume that, see [1]. So i 
>>> looked
>>> to see where tx_ring array is zeroed and didn't find it.
>>>
>>> Am i missing something here.
>>>
>>
>> It's zeroed twice.  alloc_etherdev_mqs() allocates zeroed memory and
>> then we do a memset(priv, 0, sizeof(struct mlx4_en_priv));
>>
>> regards,
>> dan carpenter
>>
> 
> We do zero (twice) on init, that's right. But I think Yuval's comment is 
> valid in case of the driver went into configuration change, or down/up, 
> that reallocates the rings. I'm double checking this.

Well, the flows in which we need to nullify the tx_rings pointer (if 
any, I still need to investigate this) is not related to this init function.

Here we're safe.

Anyway, a V2 is already submitted, please use it for your next comments. 
I think patch is OK.

Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Tariq Toukan]

On 08/05/2018 12:34 PM, Christophe JAILLET wrote:
> If the 2nd memory allocation of the loop fails, we must undo the
> memory allocation done so far.
> 
> Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
> ---
>   drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> index e0adac4a9a19..bf078244e467 100644
> --- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> +++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
> @@ -3331,7 +3331,7 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
>   		if (!priv->tx_cq[t]) {
>   			kfree(priv->tx_ring[t]);
>   			err = -ENOMEM;
> -			goto out;
> +			goto err_free_tx;
>   		}
>   	}
>   	priv->rx_ring_num = prof->rx_ring_num;
> 
Hi Christophe,

Thanks for re-sending this.

In your previous mail you referred to the call mlx4_en_destroy_netdev here:
https://elixir.bootlin.com/linux/v4.16-rc5/source/drivers/net/ethernet/mellanox/mlx4/en_main.c#L232

While I was referring to the one below, which is always called on failures:

https://elixir.bootlin.com/linux/v4.16-rc5/source/drivers/net/ethernet/mellanox/mlx4/en_netdev.c#L3587

I still believe that the err_free_tx label and its while loop is redundant.

Regards,
Tariq

[PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init_netdev()'

[Christophe JAILLET]

If the 2nd memory allocation of the loop fails, we must undo the
memory allocation done so far.

Fixes: 67f8b1dcb9ee ("net/mlx4_en: Refactor the XDP forwarding rings scheme")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
---
 drivers/net/ethernet/mellanox/mlx4/en_netdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
index e0adac4a9a19..bf078244e467 100644
--- a/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
+++ b/drivers/net/ethernet/mellanox/mlx4/en_netdev.c
@@ -3331,7 +3331,7 @@ int mlx4_en_init_netdev(struct mlx4_en_dev *mdev, int port,
 		if (!priv->tx_cq[t]) {
 			kfree(priv->tx_ring[t]);
 			err = -ENOMEM;
-			goto out;
+			goto err_free_tx;
 		}
 	}
 	priv->rx_ring_num = prof->rx_ring_num;
-- 
2.17.0