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

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Message-ID: <CAHp75VeoOj0bvGBO3PaMMD4sQTRF=rpxxLQXKeyFucpvofbV1w@mail.gmail.com>
Date:   Wed, 13 Oct 2021 12:28:24 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Yang Yingliang <yangyingliang@...wei.com>
Cc:     Joe Perches <joe@...ches.com>,
        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()

On Wed, Oct 13, 2021 at 12:17 PM Yang Yingliang
<yangyingliang@...wei.com> wrote:
> 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.

I don't think so.

  while(idx--)

is kinda idiom which is really easy to read.

I could send a v2 on your behalf.

-- 
With Best Regards,
Andy Shevchenko