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

[Joe Perches <joe@perches.com>]

On Thu, 2021-02-11 at 10:11 +0300, Dan Carpenter wrote:
> On Wed, Feb 10, 2021 at 02:28:54PM -0800, Drew Fustini wrote:
> > +	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;
> 
> We need a "ret = -EINVAL;" before the goto.  sscanf doesn't return error
> codes.  Normally we would write it like so:
> 
> 	if (sscanf(buf, "%s %s", fname, gname) != 2) {
> 		dev_err(pctldev->dev, "expected format: <function-name> <group-name>");
> 		ret = -EINVAL;
> 		goto free_gname;
> 	}
> 
> I'm going to write a Smatch check for this today.

It's a pretty frequently used style:

$ git grep -P '\w+\s*=\s+sscanf\b' | wc -l
327

A grep with -A5 seems to show most use some additional error assignment
when checking the return value.

$ git grep -P -A5 '\w+\s*=\s+sscanf\b' | grep -P '(?:return|=)\s*\-E' | wc -l
174