netdev - Re: [PATCH] net/mlx4_en: Fix an error handling path in 'mlx4_en_init

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Date:   Thu, 10 May 2018 18:03:36 +0300
From:   Tariq Toukan <tariqt@...lanox.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Yuval Shaia <yuval.shaia@...cle.com>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        davem@...emloft.net, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] net/mlx4_en: Fix an error handling path in
 'mlx4_en_init_netdev()'



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.