linux-kernel - Re: [PATCH] iio: buffer: Fix double-free in iio_buffers_alloc_sysfs_and

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Date:   Wed, 13 Oct 2021 17:17:08 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Joe Perches <joe@...ches.com>
CC:     Alexandru Ardelean <ardeleanalex@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Jonathan Cameron <jic23@...nel.org>
Subject: Re: [PATCH] iio: buffer: Fix double-free in
 iio_buffers_alloc_sysfs_and_mask()

Hi,

On 2021/10/13 4:58, Andy Shevchenko wrote:
> On Tue, Oct 12, 2021 at 8:55 PM Joe Perches <joe@...ches.com> wrote:
>> On Tue, 2021-10-12 at 23:48 +0300, Andy Shevchenko wrote:
>>> On Tue, Oct 12, 2021 at 8:43 PM Joe Perches <joe@...ches.com> wrote:
>>>> On Tue, 2021-10-12 at 23:30 +0300, Andy Shevchenko wrote:
>>>>> On Tue, Oct 12, 2021 at 2:37 PM Alexandru Ardelean
>>>>> <ardeleanalex@...il.com> wrote:
>>>>>> On Tue, Oct 12, 2021 at 12:18 PM Yang Yingliang
>>>>>> <yangyingliang@...wei.com> wrote:
> ...
>
>>>>> I prefer to see
>>>>>
>>>>> - for (; unwind_idx >= 0; unwind_idx--) {
>>>>> + while (unwind_idx--)
>>>> Not the same code as unwind_idx would be decremented before entering
>>>> the code block.
>>> It's kinda cryptic what you are pointing out.
>> Not really,
> It's. It lacks the very same "additional" words to explain what you
> meant and why.
>
>>> What's needed additionally is to change
>>>
>>> - unwind_idx = iio_dev_opaque->attached_buffers_cnt - 1;
>>> + unwind_idx = i;
>> You left out that 'additional change' above from your reply.
> Yes, that's true, but it took some time to decrypt your message.
>
>>> Of course not. See above. The usual pattern is
>>>
>>>    while (i--)
>>>      do_clean_item(i);
>> Of course, but that's not what you replied.
>> I was merely pointing out that your reply included a logic change
>> converting a loop from for to while.
> I expect that developers actually think about the changes they do and
> double check what's proposed by reviewers. If they just copy'n'paste
> whatever others propose, I wouldn't take any patch from such a
> developer.
I think in alloc path is using for loop, and in error/free path also 
using for loop is better to read the code.
>