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2018-01-02 18:26 by Karl Denninger
in Technology , 434 references Ignore this thread
Oh Oh
[Comments enabled]

Hoh hoh it really is as bad as I thought.

At best, the vulnerability could be leveraged by malware and hackers to more easily exploit other security bugs.

At worst, the hole could be abused by programs and logged-in users to read the contents of the kernel's memory. Suffice to say, this is not great. The kernel's memory space is hidden from user processes and programs because it may contain all sorts of secrets, such as passwords, login keys, files cached from disk, and so on. Imagine a piece of JavaScript running in a browser, or malicious software running on a shared public cloud server, able to sniff sensitive kernel-protected data.

No, at worst it means the hole could be abused to read hypervisor data, including encryption keys from other user's workspaces, since the Hypervisor by definition must be able to map all the guest address spaces.

In other words all cloud computing environments are insecure.

What's worse it looks like the root cause of this is that Intel cheated.  In other words their processors speculatively execute code in such a fashion that the actual access takes place before the privilege check is done.  This is good for performance but horrible for security in that it apparently can be leveraged to allow the reading of anything accessible from the hypervisor -- in other words, any other client's data.

This is a really big deal folks.  I've heard rumblings of a severe Xen problem (a common hypervisor) for a while now -- several months of relatively loud rumbling, starting with some little chirping about a year ago and change.  If this is the issue and is embedded in the architecture of the CPUs involved in modern systems then any cloud-based system will be forced to use the mitigation code which will slow it down dramatically.

Incidentally "not doing that" turns a "one machine cycle for one instruction" thing into, in many cases, a couple hundred machine cycles.  It's that bad and properly "fixed" via code workaround the performance bite will be taken on every system call.

The economic impact of this renders most so-called "cloud computing" arguments moot since we're talking performance hits of 30% or more for many common workloads -- especially those that make a lot of kernel calls!

You can bet the so-called "analysts" won't pay a bit of attention to this -- but they damn well should.  The "correct answer" is change all the CPUs to ones without this flaw -- RIGHT NOW -- but I'm sure you can figure out how happy some CIO (or CEO, or investors) will be to hear that.  The other answer is "buy 30%+ more CPUs to cover the performance deficit", which I'm sure will produce exactly the same sort of howl and should produce the same sort of hit to stock prices.

It probably won't, but it damn well should.

Then there's this -- it appears AMD's processors are not subject to this problem -- and it's been strongly hinted at by AMD that this is because they don't speculatively start execution of an instruction before determining whether it will result in a page fault.  A common complaint is that AMD's chips are somewhat slower than Intel's for "equivalent" clock speed and capability (generation, etc.)  Is the reason they were slower that Intel knowingly cheated and, if so, what implication does that have across the computing universe, especially in places where security is considered important like, oh, pretty-much everywhere?

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