Re: [PATCH] iio: buffer: Fix double-free in iio_buffers_alloc_sysfs_and_mask()

[Joe Perches]

On Tue, 2021-10-12 at 23:48 +0300, Andy Shevchenko wrote:
> On Tue, Oct 12, 2021 at 8:43 PM Joe Perches <joe@xxxxxxxxxxx> 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@xxxxxxxxx> wrote:
> > > > 
> > > > On Tue, Oct 12, 2021 at 12:18 PM Yang Yingliang
> > > > <yangyingliang@xxxxxxxxxx> wrote:
> > > > > 
> > > > > When __iio_buffer_alloc_sysfs_and_mask() failed, 'unwind_idx' should be
> > > > > set to 'i - 1' to prevent double-free when cleanup resources.
> > []
> > > 
> > > 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,

> 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.

> 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.

cheers, Joe