Re: [PATCH] drivers/net: remove network drivers' last few uses ofIRQF_SAMPLE_RANDOM

From: Matthias Andree
Date: Sun May 18 2008 - 07:03:21 EST

On Sat, 17 May 2008, Matt Mackall wrote:

> It certainly makes sense to sample network timing noise. It often does
> not make sense to assume that there's any entropy in those timing
> samples. For instance:
> - our clock resolution may be low enough that an attacker can guess our
> samples (ie it's simply HZ, very common in embedded land)
> - the bus involved (ISA, peripheral bus, even slow PCI) may have the
> same issue
> - it may be heavily correlated with some other measurement (ie network
> vs disk samples on file servers)
> We currently assume that IRQF_SAMPLE_RANDOM means 'this is a completely
> trusted unobservable entropy source' which is obviously wrong for
> network devices but is right for some other classes of device.

Without looking at code, should your summary should include
"independent of (as in non-correlated with) other sources" according to
your argument?

Matthias Andree
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