linux-kernel - Re: [PATCH] PPC: CELLEB - fix potential NULL pointer dereference

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Date:	Wed, 28 Nov 2007 13:53:46 +0300
From:	"Cyrill Gorcunov" <gorcunov@...il.com>
To:	michael@...erman.id.au
Cc:	PPCML <linuxppc-dev@...abs.org>, "Olof Johansson" <olof@...om.net>,
	"Paul Mackerras" <paulus@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Ishizaki Kou" <kou.ishizaki@...hiba.co.jp>
Subject: Re: [PATCH] PPC: CELLEB - fix potential NULL pointer dereference

On 11/28/07, Michael Ellerman <michael@...erman.id.au> wrote:
> On Mon, 2007-11-26 at 10:46 +0300, Cyrill Gorcunov wrote:
> > This patch adds checking for NULL value returned to prevent possible
> > NULL pointer dereference.
> > Also two unneeded 'return' are removed.
> >
> > Signed-off-by: Cyrill Gorcunov <gorcunov@...il.com>
> > ---
> > Any comments are welcome.
>
> I guess it's good to be paranoid, but this is a little verbose:
>
>        wi0 = of_get_property(node, "device-id", NULL);
> +       if (unlikely((!wi0))) {
> +               printk(KERN_ERR "PCI: device-id not found.\n");
> +               goto error;
> +       }
>        wi1 = of_get_property(node, "vendor-id", NULL);
> +       if (unlikely((!wi1))) {
> +               printk(KERN_ERR "PCI: vendor-id not found.\n");
> +               goto error;
> +       }
>        wi2 = of_get_property(node, "class-code", NULL);
> +       if (unlikely((!wi2))) {
> +               printk(KERN_ERR "PCI: class-code not found.\n");
> +               goto error;
> +       }
>        wi3 = of_get_property(node, "revision-id", NULL);
> +       if (unlikely((!wi3))) {
> +               printk(KERN_ERR "PCI: revision-id not found.\n");
> +               goto error;
> +       }
>
> Perhaps instead:
>
>        wi0 = of_get_property(node, "device-id", NULL);
>        wi1 = of_get_property(node, "vendor-id", NULL);
>        wi2 = of_get_property(node, "class-code", NULL);
>        wi3 = of_get_property(node, "revision-id", NULL);
>
>       if (!wi0 || !wi1 || !wi2 || !wi3) {
>               printk(KERN_ERR "PCI: Missing device tree properties.\n");
>               goto error;
>       }

Hi Michael, yes that is much better (actually I was doubt about what form of
which the checking style to use - your form is much compact but mine does
show where *exactly* the problem appeared). So 'case that is the fake driver
your form is preferred ;) Ishizaki, could you use Michael's part then?

>
>
> cheers
>
> --
> Michael Ellerman
> OzLabs, IBM Australia Development Lab
>
> wwweb: http://michael.ellerman.id.au
> phone: +61 2 6212 1183 (tie line 70 21183)
>
> We do not inherit the earth from our ancestors,
> we borrow it from our children. - S.M.A.R.T Person
>
>

Cyrill
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