linux-kernel - Re: [PATCH] iio: potentiometer: ds1803: remove VLA usage

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Message-ID: <ef7f3979-afca-73d2-63f6-c3a380452a91@embeddedor.com>
Date:   Tue, 13 Mar 2018 12:07:00 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Himanshu Jha <himanshujha199640@...il.com>
Cc:     Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: potentiometer: ds1803: remove VLA usage



On 03/13/2018 11:59 AM, Himanshu Jha wrote:
> On Tue, Mar 13, 2018 at 11:31:19AM -0500, Gustavo A. R. Silva wrote:
>>
>>
>> On 03/13/2018 11:24 AM, Himanshu Jha wrote:
>>> Hi Gustavo,
>>>
>>> On Tue, Mar 13, 2018 at 10:23:43AM -0500, Gustavo A. R. Silva wrote:
>>>> In preparation to enabling -Wvla, remove VLA. In this particular
>>>> case use macro ARRAY_SIZE so the length of array _result_ can be
>>>> computed at preprocessing time.
>>>>
>>>> The use of stack Variable Length Arrays needs to be avoided, as they
>>>> can be a vector for stack exhaustion, which can be both a runtime bug
>>>> or a security flaw. Also, in general, as code evolves it is easy to
>>>> lose track of how big a VLA can get. Thus, we can end up having runtime
>>>> failures that are hard to debug.
>>>>
>>>> Also, fixed as part of the directive to remove all VLAs from
>>>> the kernel: https://lkml.org/lkml/2018/3/7/621
>>>>
>>>> Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
>>>> ---
>>>
>>> It is already applied as I had sent the patch few days ago.
>>> https://lkml.org/lkml/2018/3/10/164
>>>
>>> I specifically CC'ed you and Kees to avoid the patch collisions.
>>>
>>
>> I see. Can you please update this spreadsheet:
>>
>> https://docs.google.com/spreadsheets/d/1OcfyKK8pJ24esYhSEsW4Q2boZE7UTGbYsSEEtFXf7U0/edit
> 
> Updated!
> 
> Also,
> 
> drivers/iio/humidity/hts221_i2c.c:43:2: warning: ISO C90
> forbids variable length array ‘send’ [-Wvla]
> 
> This was already removed in recent commit when regmap API was used.
> 
> "6217792 iio: humidity: hts221: add regmap API support"
> 
> For this I added a short note in the *Notes* column.
> 

Awesome.

Thank you
--
Gustavo