Hi Simon,

On Apr 15, 2011, at 19:53 , Simon Wilkinson wrote:

> One of the issues that comes up from time to time is what actually 
> constitutes a bug worthy of a security advisory. Sometimes this is really 
> clear cut, but in other areas, in particular in relation to our Unix kernel 
> modules, the dividing line is significantly less clear. Getting this right is 
> important. On one hand, we have an obligation to make people aware quickly 
> when there is an issue that affects the security of their systems. On the 
> other hand, when a change addresses a security issue we have historically 
> made a release containing just that change. Making security releases is 
> expensive and time consuming - it removes developer effort from all of the 
> other things that we want to get done, and delays the arrival of releases 
> that actually contain new code.
> 
> The problem is that any programming mistake in our kernel module will 
> generally result either in the machine locking up, or in the AFS filesystem 
> becoming unusable. We generally find out about these mistakes because a local 
> user triggers them, so from a security point of view, virtually all of them 
> are a local denial of service attack.

the problem is that "DOS only" problems tend to become "privilege escalation" 
ones once a smart attacker looks at them. And often in ways the 
developers/maintainers don't expect.

> My proposal, going forwards, is to not produce security advisories or 
> releases for these local denial of service attacks.

Whenever you're completely confident that there's no way to exploit the bug for 
privilege escalation, that's fine.

> Local issues that can result in privilege escalation, or denial of service 
> attacks that can be performed by those outside a sites infrastructure would 
> still result in advisories.
> 
> My supplemental question, is just how much use the "security releases" 
> actually are. Most of our packagers ignore them, in favour of pulling the 
> patches that we release with the advisory into their packaging. Is just 
> providing these patches sufficient?

I have applied, as well as backported, them to packages I've supported a few 
times in the past. Yes, they are useful.

> Is there actually a demand for a "super-stable" point update that just 
> contains the security code, or is it acceptable to provide the security fix 
> as part of a normal stable release?
> 
> I'd welcome feedback about both of these.

It really depends on what you call a "normal stable release". In particular, 
1.4.8 was not a stable release IMO. Subsequent releases weren't either, at 
least up to 1.4.11. And 1.4.12 and 1.4.14 are still broken for one of our most 
important use cases - 1.4.7 handled it well.

So, frankly, the collected security fixes against 1.4.7 would be extremely 
useful. We'd probably start running this "super stable point release" tomorrow 
on >1000 systems if it were available.

Hope this helps,
        Stephan

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