linux-kernel - Re: [PATCH 1/3] gpio: Fix a potential abuse of seq

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Message-ID: <CAMuHMdWEuWrfj3p0pX7FX6AgOKryFUnCEBRhPkhvnSEkMwThpQ@mail.gmail.com>
Date: Wed, 20 Nov 2024 12:04:39 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: David Wang <00107082@....com>
Cc: linus.walleij@...aro.org, brgl@...ev.pl, kees@...nel.org, 
	linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] gpio: Fix a potential abuse of seq_printf() format string

Hi David,

On Wed, Nov 20, 2024 at 10:15 AM David Wang <00107082@....com> wrote:
> Using device name as format string of seq_printf() is prone to
> "Format string attack", opens possibility for exploitation.
> Seq_puts() is safer and more efficient.
>
> Signed-off-by: David Wang <00107082@....com>

Thanks for your patch!

> --- a/drivers/gpio/gpio-aspeed-sgpio.c
> +++ b/drivers/gpio/gpio-aspeed-sgpio.c
> @@ -420,7 +420,7 @@ static void aspeed_sgpio_irq_print_chip(struct irq_data *d, struct seq_file *p)
>         int offset;
>
>         irqd_to_aspeed_sgpio_data(d, &gpio, &bank, &bit, &offset);
> -       seq_printf(p, dev_name(gpio->dev));
> +       seq_puts(p, dev_name(gpio->dev));

If we want to add the missing space here, the code has to be changed
to use seq_printf(..., " %s", ...) again.

However, it might be simpler to move this to the core. I.e. add an
unconditional seq_putc(p, ' ') to show_interrupts()[1], and drop the
spaces from all callbacks and from the fallbacks in show_interrupts().

[1] https://elixir.bootlin.com/linux/v6.12/source/kernel/irq/proc.c#L503

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds