Re: [PATCH v2 2/3] pinctrl: renesas: rzv2m: Fix NULL pointer dereference in rzv2m_dt_subnode_to_map()

[Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>]

Hi Biju,

On Tue, Aug 15, 2023 at 9:56 AM Biju Das <biju.das.jz@xxxxxxxxxxxxxx> wrote:
> Fix the below random NULL pointer crash during boot by serializing
> groups and functions creation in rzv2m_dt_subnode_to_map() with
> mutex lock.
>
> Crash logs:
>  pc : __pi_strcmp+0x20/0x140
>  lr : pinmux_func_name_to_selector+0x68/0xa4
>  Call trace:
>  __pi_strcmp+0x20/0x140
>  pinmux_generic_add_function+0x34/0xcc
>  rzv2m_dt_subnode_to_map+0x2e4/0x418
>  rzv2m_dt_node_to_map+0x15c/0x18c
>  pinctrl_dt_to_map+0x218/0x37c
>  create_pinctrl+0x70/0x3d8
>
> Fixes: 92a9b8252576 ("pinctrl: renesas: Add RZ/V2M pin and gpio controller driver")
> Cc: stable@xxxxxxxxxx
> Signed-off-by: Biju Das <biju.das.jz@xxxxxxxxxxxxxx>
> ---
> v1->v2:
>  * Updated crash logs as per submitting patches doc.

Thanks for your patch!

> --- a/drivers/pinctrl/renesas/pinctrl-rzv2m.c
> +++ b/drivers/pinctrl/renesas/pinctrl-rzv2m.c
> @@ -14,6 +14,7 @@
>  #include <linux/gpio/driver.h>
>  #include <linux/io.h>
>  #include <linux/module.h>
> +#include <linux/mutex.h>
>  #include <linux/of.h>
>  #include <linux/platform_device.h>
>  #include <linux/spinlock.h>
> @@ -124,6 +125,7 @@ struct rzv2m_pinctrl {
>         struct pinctrl_gpio_range       gpio_range;
>
>         spinlock_t                      lock;
> +       struct mutex                    mutex; /* serialize adding groups and functions */

I guess it's not too late to add a comment to the other lock?

>  };
>
>  static const unsigned int drv_1_8V_group2_uA[] = { 1800, 3800, 7800, 11000 };
> @@ -322,10 +324,12 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
>                 name = np->name;
>         }
>
> +       mutex_lock(&pctrl->mutex);

I think this is too late, as krealloc_array() above has already released
the old map.

>         /* Register a single pin group listing all the pins we read from DT */
>         gsel = pinctrl_generic_add_group(pctldev, name, pins, num_pinmux, NULL);
>         if (gsel < 0) {
>                 ret = gsel;
> +               mutex_unlock(&pctrl->mutex);

Please add a new label below, to avoid adding a call to mutex_unlock()
here.

>                 goto done;
>         }
>
> @@ -340,6 +344,8 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
>                 goto remove_group;
>         }
>
> +       mutex_unlock(&pctrl->mutex);
> +
>         maps[idx].type = PIN_MAP_TYPE_MUX_GROUP;
>         maps[idx].data.mux.group = name;
>         maps[idx].data.mux.function = name;
> @@ -351,6 +357,7 @@ static int rzv2m_dt_subnode_to_map(struct pinctrl_dev *pctldev,
>
>  remove_group:
>         pinctrl_generic_remove_group(pctldev, gsel);

^^ new label here.

> +       mutex_unlock(&pctrl->mutex);
>  done:
>         *index = idx;
>         kfree(configs);

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

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