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

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Date:	Wed, 28 Nov 2007 20:48:53 +1100
From:	Michael Ellerman <michael@...erman.id.au>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	PPCML <linuxppc-dev@...abs.org>, Olof Johansson <olof@...om.net>,
	Paul Mackerras <paulus@...ba.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PPC: CELLEB - fix potential NULL pointer dereference

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;
       }


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

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