netdev - Re: potential overflow in de4x5.c

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Message-ID: <20100104072844.GB518@lackof.org>
Date:	Mon, 4 Jan 2010 00:28:44 -0700
From:	Grant Grundler <grundler@...isc-linux.org>
To:	Dan Carpenter <error27@...il.com>
Cc:	Grant Grundler <grundler@...isc-linux.org>,
	Kyle McMartin <kyle@...artin.ca>, netdev@...r.kernel.org
Subject: Re: potential overflow in de4x5.c

On Sun, Jan 03, 2010 at 12:13:56PM +0200, Dan Carpenter wrote:
> Hi I found this using smatch (http://repo.or.cz/w/smatch.git).
> 
> drivers/net/tulip/de4x5.c
>   4772          lp->active = *p++;
>   4773          if (MOTO_SROM_BUG) lp->active = 0;
>   4774          lp->phy[lp->active].gep = (*p ? p : NULL); p += (2 * (*p) + 1);
> 
> lp->phy is an array of size 8.
> 
> MOTO_SROM_BUG is defined like this. 
> 
> #define MOTO_SROM_BUG    (lp->active == 8 && (get_unaligned_le32(dev->dev_addr) & 0x00ffffff) == 0x3e0008)
> 
> If lp->active == 8 then we have a buffer overflow.

Dan,
When does the overflow actually occur?

That code is reseting the value to work around a specific SROM bug:
   http://lists.ozlabs.org/pipermail/linuxppc-dev/1999-March/001421.html

If you want to make the "input validation" more robust, that would be fine with me.
But smatch hasn't convinced me there is a bug here.

thanks,
grant

> 
> regards,
> dan carpenter
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