Re: potential overflow in de4x5.c

On Mon, Jan 04, 2010 at 12:28:44AM -0700, Grant Grundler wrote:

On Sun, Jan 03, 2010 at 12:13:56PM +0200, Dan Carpenter wrote:

quoted

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.

BTW, someone suggested to fix up this same bit of code before:
   http://www.mail-archive.com/netdev@vger.kernel.org/msg09838.html

And I'm not sure why that patch wasn't accepted then either. Patch looks fine to me.

thanks,
grant