Date: Sun, 3 Jun 2018 15:37:35 +0200 From: Greg KH <gregkh@...uxfoundation.org> To: procmem <procmem@...eup.net> Cc: kernel-hardening@...ts.openwall.com Subject: Re: Nethammer and kernel network drivers On Sun, Jun 03, 2018 at 01:23:28PM +0000, procmem wrote: > > > Greg KH: > > On Sat, Jun 02, 2018 at 05:41:09PM +0000, procmem wrote: > >> Hello. Daniel provided more details on the problematic areas of the > >> kernel and I quote what he said verbatim: > >> > >> > >>> We have only found very outdated network drivers using clflush (old > >>> windows ndis code). On ARM there are many drivers using uncached memory. > >>> However, we have so far failed to produce enough memory traffic on ARM > >>> to trigger a bit flip with Nethammer on any ARM device. > >>> It should be possible though if you can make the ARM device handle > >>>> =300MBit/s. > >>> And that's the most plausible scenario. > >>> > >>> Anyway, searching for clflush or use of uncached memory is a good idea > >>> to locate the critical spots. > >>> > >>> Intel CAT is (we believe) not used anywhere yet. And we must be careful > >>> when it gets to the point where we introduce usage of CAT for QoS > >>> mechanisms. > >>> > >>> However, my intuition tells me that most systems are not even vulnerable > >>> to Rowhammer in the first place. Although the only prevalence studies we > >>> have suggest otherwise (they find 60-80% are affected). > > > > So Linux is not vulnerable to this at all? That's good to know, thanks > > for following up with this. > > > > greg k-h > > > > I interpreted this to mean that there is a major problem with ARM > drivers but the only backstop is the current gen of hardware being > underpowered. Really? There are ARM servers now that can do really fast networking, yet those drivers do not seem to have this problem from what I can see. Am I missing something here? > Also it would be best to put a kernel comment about sec implications > of Intel CAT for those who want to enable/use it IMHO. Patches are always gladly accepted :) thanks, greg k-h
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