netdev - Re: [PATCH] net/mlx4_en: fix off by one in error handling

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Message-ID: <2f37b3b3-af5d-6bf9-e972-1ddcb4535682@gmail.com>
Date:   Thu, 15 Sep 2016 15:18:32 +0300
From:   Tariq Toukan <ttoukan.linux@...il.com>
To:     Sebastian Ott <sebott@...ux.vnet.ibm.com>
Cc:     Yishai Hadas <yishaih@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>, netdev@...r.kernel.org,
        linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net/mlx4_en: fix off by one in error handling



On 14/09/2016 7:08 PM, Sebastian Ott wrote:
> On Wed, 14 Sep 2016, Tariq Toukan wrote:
>> On 14/09/2016 4:53 PM, Sebastian Ott wrote:
>>> On Wed, 14 Sep 2016, Tariq Toukan wrote:
>>>> On 14/09/2016 2:09 PM, Sebastian Ott wrote:
>>>>> If an error occurs in mlx4_init_eq_table the index used in the
>>>>> err_out_unmap label is one too big which results in a panic in
>>>>> mlx4_free_eq. This patch fixes the index in the error path.
>>>> You are right, but your change below does not cover all cases.
>>>> The full solution looks like this:
>>>>
>>>> @@ -1260,7 +1260,7 @@ int mlx4_init_eq_table(struct mlx4_dev *dev)
>>>>                                                eq);
>>>>                   }
>>>>                   if (err)
>>>> -                       goto err_out_unmap;
>>>> +                       goto err_out_unmap_excluded;
>>> In this case a call to mlx4_create_eq failed. Do you really have to call
>>> mlx4_free_eq for this index again?
>> We agree on this part, that's why here we should goto the _excluded_ label.
>> For all other parts, we should not exclude the eq in the highest index, and
>> thus we goto the _non_excluded_ label.
> But that's exactly what the original patch does. If the failure is within
> the for loop at index i, we do the cleanup starting at index i-1. If the
> failure is after the for loop then i == dev->caps.num_comp_vectors + 1
> and we do the cleanup starting at index i == dev->caps.num_comp_vectors.
>
> In the latter case your patch would have an out of bounds array access.
Indeed. Agreed.

> Regards,
> Sebastian
>

Reviewed-by: Tariq Toukan <tariqt@...lanox.com>

Thanks!