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

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Date:   Wed, 10 Feb 2021 22:05:29 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     kbuild@...ts.01.org, Drew Fustini <drew@...gleboard.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tony Lindgren <tony@...mide.com>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Pantelis Antoniou <pantelis.antoniou@...sulko.com>,
        Jason Kridner <jkridner@...gleboard.org>,
        Robert Nelson <robertcnelson@...gleboard.org>,
        kbuild test robot <lkp@...el.com>, kbuild-all@...ts.01.org
Subject: Re: [PATCH v2 2/2] pinctrl: pinmux: Add pinmux-select debugfs file

On Wed, Feb 10, 2021 at 07:39:16PM +0100, Geert Uytterhoeven wrote:
> Hi Dan,
> 
> On Wed, Feb 10, 2021 at 7:21 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  694    buf = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME * 2, GFP_KERNEL);
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  695    if (!buf)
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  696            return -ENOMEM;
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  697
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  698    fname = devm_kzalloc(pctldev->dev, PINMUX_MAX_NAME, GFP_KERNEL);
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  699    if (!fname) {
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  700            ret = -ENOMEM;
> > 99b2f99aa41aa7 Drew Fustini  2021-02-09  701            goto free_buf;
> >
> > The gotos are out of order.  They should be in mirror/reverse order of
> > the allocations:
> >
> > free_gmane:
> >         devm_kfree(pctldev->dev, gname);
> > free_fname:
> >         devm_kfree(pctldev->dev, fname);
> > free_buf:
> >         devm_kfree(pctldev->dev, buf);
> >
> > But also why do we need to use devm_kfree() at all?  I thought the whole
> > point of devm_ functions was that they are garbage collected
> > automatically for you.  Can we not just delete all error handling and
> > return -ENOMEM here?
> 
> No, because the lifetime of the objects allocated here does not match the
> lifetime of dev.  If they're not freed here, they will only be freed when the
> device is unbound.  As the user can access the sysfs files at will, he can
> OOM the system.
> 

Then why not use vanilla kmalloc()?

regards,
dan carpenter