From: Rosen Penev <rosenp@gmail.com>
To: Kees Cook <kees@kernel.org>
Cc: linux-gpio@vger.kernel.org,
Bamvor Jian Zhang <bamv2005@gmail.com>,
Linus Walleij <linusw@kernel.org>,
Bartosz Golaszewski <brgl@kernel.org>,
"Gustavo A. R. Silva" <gustavoars@kernel.org>,
open list <linux-kernel@vger.kernel.org>,
"open list:KERNEL HARDENING (not covered by other
areas):Keyword:b__counted_by(_le|_be)?b"
<linux-hardening@vger.kernel.org>
Subject: Re: [PATCH] gpio: mockup: allocate lines with main struct
Date: Fri, 20 Mar 2026 16:00:04 -0700 [thread overview]
Message-ID: <CAKxU2N8ZZp5fcCWfMaqZ9VKwNQ3a06fsQPXpBQa-d1N07zPGng@mail.gmail.com> (raw)
In-Reply-To: <202603201104.8D7B8A1@keescook>
On Fri, Mar 20, 2026 at 11:10 AM Kees Cook <kees@kernel.org> wrote:
>
> On Wed, Mar 18, 2026 at 05:05:58PM -0700, Rosen Penev wrote:
> > Remove no longer needed kcalloc to simplify allocation.
> >
> > Added __counted_by along with a counting variable to get extra runtime
> > analysis.
> >
> > Signed-off-by: Rosen Penev <rosenp@gmail.com>
> > ---
> > drivers/gpio/gpio-mockup.c | 17 ++++++++---------
> > 1 file changed, 8 insertions(+), 9 deletions(-)
> >
> > diff --git a/drivers/gpio/gpio-mockup.c b/drivers/gpio/gpio-mockup.c
> > index a7d69f3835c1..a907ce28cbbb 100644
> > --- a/drivers/gpio/gpio-mockup.c
> > +++ b/drivers/gpio/gpio-mockup.c
> > @@ -52,10 +52,11 @@ struct gpio_mockup_line_status {
> >
> > struct gpio_mockup_chip {
> > struct gpio_chip gc;
> > - struct gpio_mockup_line_status *lines;
> > struct irq_domain *irq_sim_domain;
> > struct dentry *dbg_dir;
> > struct mutex lock;
> > + int nr_lines;
> > + struct gpio_mockup_line_status lines[] __counted_by(nr_lines);
> > };
>
> In the cases where a new counter variable is being added to the struct,
> I think it might be better to have those be unsigned.
>
> >
> > struct gpio_mockup_dbgfs_private {
> > @@ -436,15 +437,18 @@ static int gpio_mockup_probe(struct platform_device *pdev)
> > if (rv)
> > name = dev_name(dev);
> >
> > - chip = devm_kzalloc(dev, sizeof(*chip), GFP_KERNEL);
> > + chip = devm_kzalloc(dev, struct_size(chip, lines, ngpio), GFP_KERNEL);
> > if (!chip)
> > return -ENOMEM;
> >
> > - mutex_init(&chip->lock);
> > + chip->nr_lines = ngpio;
>
> Besides the new variable being meaningless for negative values, there's
> a strong hint about its type even from the counter used to perform the
> calculation (u16):
>
> static int gpio_mockup_probe(struct platform_device *pdev)
> {
> ...
> u16 ngpio;
> ...
> rv = device_property_read_u16(dev, "nr-gpios", &ngpio);
> ...
> gc->ngpio = ngpio;
> ...
> chip->lines = devm_kcalloc(dev, gc->ngpio,
> sizeof(*chip->lines), GFP_KERNEL);
>
> But this begs the question: why add nr_lines when ngpio is already part
> of the struct:
Maintainers for some inexplicable reason want an extra variable for
__counted_by works.
>
> struct gpio_chip {
> ...
> u16 ngpio;
>
>
> ?
>
> -Kees
>
> --
> Kees Cook
next prev parent reply other threads:[~2026-03-20 23:00 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-19 0:05 [PATCH] gpio: mockup: allocate lines with main struct Rosen Penev
2026-03-20 13:28 ` Linus Walleij
2026-03-20 18:10 ` Kees Cook
2026-03-20 23:00 ` Rosen Penev [this message]
2026-03-23 10:00 ` Bartosz Golaszewski
2026-03-23 16:43 ` Rosen Penev
2026-03-24 9:16 ` Bartosz Golaszewski
2026-03-24 15:51 ` Rosen Penev
2026-03-24 15:54 ` Bartosz Golaszewski
2026-03-24 15:56 ` Rosen Penev
2026-03-24 17:16 ` Bartosz Golaszewski
2026-03-24 18:25 ` Rosen Penev
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