Re: [PATCH v4 2/2] pinctrl: pinmux: Add pinmux-select debugfs file

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

On Wed, Feb 10, 2021 at 02:28:54PM -0800, Drew Fustini wrote:
> Add "pinmux-select" to debugfs which will activate a function and group
> when "<function-name group-name>" are written to the file. The write
> operation pinmux_select() handles this by checking that the names map to
> 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 and group pinmux-i2c1-pins:
> 
> echo "pinmux-i2c1 pinmux-i2c1-pins" > pinmux-select
> 
> Signed-off-by: Drew Fustini <drew@xxxxxxxxxxxxxxx>
> ---
>  drivers/pinctrl/pinmux.c | 107 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 107 insertions(+)
> 
> diff --git a/drivers/pinctrl/pinmux.c b/drivers/pinctrl/pinmux.c
> index c651b2db0925..23fa32f0a067 100644
> --- a/drivers/pinctrl/pinmux.c
> +++ b/drivers/pinctrl/pinmux.c
> @@ -673,6 +673,111 @@ void pinmux_show_setting(struct seq_file *s,
>  DEFINE_SHOW_ATTRIBUTE(pinmux_functions);
>  DEFINE_SHOW_ATTRIBUTE(pinmux_pins);
>  
> +#define PINMUX_MAX_NAME 64
> +static ssize_t pinmux_select(struct file *file, const char __user *user_buf,
> +				   size_t len, loff_t *ppos)
> +{
> +	struct seq_file *sfile = file->private_data;
> +	struct pinctrl_dev *pctldev = sfile->private;
> +	const struct pinmux_ops *pmxops = pctldev->desc->pmxops;
> +	const char *const *groups;
> +	char *buf, *fname, *gname;
> +	unsigned int num_groups;
> +	int fsel, gsel, ret;
> +
> +	if (len > (PINMUX_MAX_NAME * 2)) {
> +		dev_err(pctldev->dev, "write too big for buffer");
> +		return -EINVAL;
> +	}
> +
> +	buf = kzalloc(PINMUX_MAX_NAME * 2, GFP_KERNEL);
> +	if (!buf)
> +		return -ENOMEM;
> +
> +	fname = kzalloc(PINMUX_MAX_NAME, GFP_KERNEL);
> +	if (!fname) {
> +		ret = -ENOMEM;
> +		goto free_buf;
> +	}
> +
> +	gname = kzalloc(PINMUX_MAX_NAME, GFP_KERNEL);
> +	if (!buf) {
> +		ret = -ENOMEM;
> +		goto free_fname;
> +	}
> +
> +	ret = strncpy_from_user(buf, user_buf, PINMUX_MAX_NAME * 2);
> +	if (ret < 0) {
> +		dev_err(pctldev->dev, "failed to copy buffer from userspace");
> +		goto free_gname;
> +	}
> +	buf[len-1] = '\0';
> +
> +	ret = sscanf(buf, "%s %s", fname, gname);
> +	if (ret != 2) {
> +		dev_err(pctldev->dev, "expected format: <function-name> <group-name>");
> +		goto free_gname;
> +	}
> +
> +	fsel = pinmux_func_name_to_selector(pctldev, fname);
> +	if (fsel < 0) {
> +		dev_err(pctldev->dev, "invalid function %s in map table\n", fname);
> +		ret = -EINVAL;
> +		goto free_gname;
> +	}
> +
> +	ret = pmxops->get_function_groups(pctldev, fsel, &groups, &num_groups);
> +	if (ret) {
> +		dev_err(pctldev->dev, "no groups for function %d (%s)", fsel, fname);
> +		goto free_gname;
> +
> +	}
> +
> +	ret = match_string(groups, num_groups, gname);
> +	if (ret < 0) {
> +		dev_err(pctldev->dev, "invalid group %s", gname);
> +		goto free_gname;
> +	}
> +
> +	ret = pinctrl_get_group_selector(pctldev, gname);
> +	if (ret < 0) {
> +		dev_err(pctldev->dev, "failed to get group selectorL %s", gname);
> +		goto free_gname;
> +	}
> +	gsel = ret;
> +
> +	ret = pmxops->set_mux(pctldev, fsel, gsel);
> +	if (ret) {
> +		dev_err(pctldev->dev, "set_mux() failed: %d", ret);
> +		goto free_gname;
> +	}
> +
> +	return len;
> +
> +free_gname:
> +	devm_kfree(pctldev->dev, gname);
> +free_fname:
> +	devm_kfree(pctldev->dev, fname);
> +free_buf:
> +	devm_kfree(pctldev->dev, buf);

Ugh...  I honestly thought Smatch was supposed to print a warning when
you used devm_kfree() on kzalloc()ed memory, but I guess the warning is
only the other way around.

Smatch does complain about it as a leak because it was expecting a
regular free.

drivers/pinctrl/pinmux.c:330 pinmux_func_name_to_selector() warn: potential NULL parameter dereference 'fname'
drivers/pinctrl/pinmux.c:764 pinmux_select() warn: possible memory leak of 'gname'
drivers/pinctrl/pinmux.c:764 pinmux_select() warn: sscanf doesn't return error codes
drivers/pinctrl/pinmux.c:764 pinmux_select() warn: returning success when sscanf failed

And what about the success path?  Shouldn't we free these on the success
path as well?

regards,
dan carpenter