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

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Message-ID: <7b4105ca8671a2962910deb5418a934bf07d1458.camel@perches.com>
Date:   Wed, 10 Feb 2021 23:24:23 -0800
From:   Joe Perches <joe@...ches.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Drew Fustini <drew@...gleboard.org>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tony Lindgren <tony@...mide.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>
Subject: Re: [PATCH v4 2/2] pinctrl: pinmux: Add pinmux-select debugfs file

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