Re: [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file

Andy Shevchenko
2021-02-10T10:05:45Z

On Wed, Feb 10, 2021 at 9:50 AM Drew Fustini <drew@beagleboard.org> wrote:
>
> Add "pinmux-select" to debugfs which will activate a function and group
> when 2 integers "<function-selector> <group-selector>" are written to
> the file. The write operation pinmux_select() handles this by checking
> if fsel and gsel are valid selectors and then calling ops->set_mux().
>
> The existing "pinmux-functions" debugfs file lists the pin functions
> registered for the pin controller. For example:
>
> function: pinmux-uart0, groups = [ pinmux-uart0-pins ]
> function: pinmux-mmc0, groups = [ pinmux-mmc0-pins ]
> function: pinmux-mmc1, groups = [ pinmux-mmc1-pins ]
> function: pinmux-i2c0, groups = [ pinmux-i2c0-pins ]
> function: pinmux-i2c1, groups = [ pinmux-i2c1-pins ]
> function: pinmux-spi1, groups = [ pinmux-spi1-pins ]
>
> To activate function pinmux-i2c1 (fsel 4) and group pinmux-i2c1-pins
> (gsel 4):
>
> echo '4 4' > pinmux-select

...

> DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
>

> +

One blank line (existed) is enough.

> +#define PINMUX_MAX_NAME 64

...

> + buf = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME * 2, GFP_KERNEL);

You have to (re-)read documentation about Device Managed Resources.
Keyword here is *device*! Pay attention to it. TL;DR: misuse of device
managed resources here.
Potentially memory exhausting (local DoS attack), but see below.

> + if (!buf)
> + return -ENOMEM;

...

> + devm_kfree(pctldev->dev, buf);

Calling devm_kfree() or other devm_*() release kinda APIs is a red
flag in 99%. See above.

--
With Best Regards,
Andy Shevchenko