Re: unhelpful and somewhat scary r8169 boot message in a security fix

From: David Miller
Date: Fri Apr 02 2010 - 17:36:34 EST

From: Nix <nix@xxxxxxxxxxxxx>
Date: Fri, 02 Apr 2010 16:19:13 +0100

> So I was doing a test-boot of to see if my hang-on-suspend
> Radeon DRM regression (fdo bug 26872) was cured (it wasn't), when a
> new message appeared at bootup, the second of those below:
> [ 8.766768] r8169: fastnet: link up
> [ 8.791231] WARNING! Changing of MTU on this NICMay lead to frame reception errors!
> (which appeared when I set the MTU on my r8169 to 7200.)
> Not only is this message plainly misformatted :)

Formating has been fixed in the net-2.6 tree yesterday.

> but it does not explain *why* changing the MTU is suddenly so bad,
> when it's worked forever before now without flaw, with no sign of
> any sort of corruption. Why should we be confined to non-jumbo
> frames? What are the effects if we do change MTU?

Have a look at CVE-2009-4537

It's a remotely exploitable memory corruptor and potential
root hole.
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