linux-kernel - Re: [PATCH v4] gpio: sim: fix an invalid _

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Message-ID: <ZQlPre4nnydZyDAm@sol>
Date:   Tue, 19 Sep 2023 15:37:17 +0800
From:   Kent Gibson <warthog618@...il.com>
To:     brgl@...ev.pl
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Alexey Dobriyan <adobriyan@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        akpm@...ux-foundation.org, linux-gpio@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: Re: [PATCH v4] gpio: sim: fix an invalid __free() usage

On Tue, Sep 19, 2023 at 12:31:36AM -0700, brgl@...ev.pl wrote:
> On Mon, 18 Sep 2023 17:31:36 +0200, Andy Shevchenko
> <andriy.shevchenko@...ux.intel.com> said:
> > On Mon, Sep 18, 2023 at 04:55:33PM +0200, Bartosz Golaszewski wrote:
> >> From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
> >>
> >> gpio_sim_make_line_names() returns NULL or ERR_PTR() so we must not use
> >> __free(kfree) on the returned address. Split this function into two, one
> >> that determines the size of the "gpio-line-names" array to allocate and
> >> one that actually sets the names at correct offsets. The allocation and
> >> assignment of the managed pointer happens in between.
> >
> > ...
> >
> >> +	unsigned int size = 0;
> >>
> >>  	list_for_each_entry(line, &bank->line_list, siblings) {
> >> +		if (!line->name || (line->offset >= bank->num_lines))
> >>  			continue;
> >>
> >> +		size = line->offset + 1;
> >>  	}
> >>
> >> +	return size;
> >
> > So, now the function iterates over all lines and returns the size of the last
> > match, correct?
> >
> > Why not
> >
> > 	list_for_each_entry_reversed() {
> > 		if (line->name && ())
> > 			break;
> > 	}
> >
> > 	return size;
> >
> > ?
> 
> Because the line objects are not sorted by offset. They are added at the end
> of the list in the order the user creates their corresponding configfs groups.
> 

Then your patch is also broken as it uses the last named entry,
not the named entry with the greatest offset??

Cheers,
Kent.