linux-kernel - Re: [PATCH][next] pinctrl: pinctrl-single: add allocation failure checking of saved

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Message-ID: <20180607073543.GP13775@localhost>
Date:   Thu, 7 Jun 2018 09:35:43 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Colin King <colin.king@...onical.com>,
        Tony Lindgren <tony@...mide.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        kernel-janitors@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        Haojian Zhuang <haojian.zhuang@...aro.org>,
        Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH][next] pinctrl: pinctrl-single: add allocation failure
 checking of saved_vals

On Wed, Jun 06, 2018 at 07:02:03PM +0300, Andy Shevchenko wrote:
> On Wed, Jun 6, 2018 at 4:43 PM, Colin King <colin.king@...onical.com> wrote:
> > From: Colin Ian King <colin.king@...onical.com>
> >
> > Currently saved_vals is being allocated and there is no check for
> > failed allocation (which is more likely than normal when using
> > GFP_ATOMIC).  Fix this by checking for a failed allocation and
> > propagating this error return down the the caller chain.
> >
> > Detected by CoverityScan, CID#1469841 ("Dereference null return value")
> >
> > Fixes: 88a1dbdec682 ("pinctrl: pinctrl-single: Add functions to save and restore pinctrl context")
> > Signed-off-by: Colin Ian King <colin.king@...onical.com>
> > ---
> >  drivers/pinctrl/pinctrl-single.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/pinctrl/pinctrl-single.c b/drivers/pinctrl/pinctrl-single.c
> > index 9c3c00515aa0..0905ee002041 100644
> > --- a/drivers/pinctrl/pinctrl-single.c
> > +++ b/drivers/pinctrl/pinctrl-single.c
> > @@ -1588,8 +1588,11 @@ static int pcs_save_context(struct pcs_device *pcs)
> >
> >         mux_bytes = pcs->width / BITS_PER_BYTE;
> >
> > -       if (!pcs->saved_vals)
> > +       if (!pcs->saved_vals) {
> >                 pcs->saved_vals = devm_kzalloc(pcs->dev, pcs->size, GFP_ATOMIC);
> 
> > +               if (!pcs->saved_vals)
> > +                       return -ENOMEM;
> 
> Wouldn't make sense to move it out of the first condition?
> 
> Something like
> 
> if (!foo)
>  foo = ...malloc(...);
> if (!foo)
>  return ...

No, checking for NULL immediately after the allocation is more obvious
and easier to parse.

Johan