Another Day, Another Intel CPU Security Hole: Lazy State (zdnet.com)

Steven J. Vaughan-Nichols, writing for ZDNet: The latest Intel revelation, Lazy FP state restore, can theoretically pull data from your programs, including encryption software, from your computer regardless of your operating system. Like its forebears, this is a speculative execution vulnerability. In an interview, Red Hat Computer Architect Jon Masters explained: "It affects Intel designs similar to variant 3-a of the previous stuff, but it's NOT Meltdown." Still, "it allows the floating point registers to be leaked from another process, but alas that means the same registers as used for crypto, etc." Lazy State does not affect AMD processors.

This vulnerability exists because modern CPUs include many registers (internal memory) that represent the state of each running application. Saving and restoring this state when switching from one application to another takes time. As a performance optimization, this may be done "lazily" (i.e., when needed) and that is where the problem hides. This vulnerability exploits "lazy state restore" by allowing an attacker to obtain information about the activity of other applications, including encryption operations. Further reading: Twitter thread by security researcher Colin Percival, BleepingComputer, and HotHardware.

Comments

"regardless of your operating system"

[QuietLagoon]

Yet the linked article says

...For some operating systems, the fix is already in. Red Hat Enterprise Linux (RHEL) 7 automatically defaults to (safe) "eager" floating point restore on all recent x86-64 microprocessors (approximately 2012 and later) implementing the "XSAVEOPT" extension. Therefore, most RHEL 7 users won't need to take any corrective action.

Other operating systems believed to be safe are any Linux version using the 2016's Linux 4.9 or newer kernel. The Linux kernel developers are patching older kernels. Most versions of Windows, including Server 2016 and Windows 10. are believed to be safe. If you're still using Windows Server 2008, however, you will need a patch. The latest editions of OpenBSD and DragonflyBSD are immune, and there's a fix available for FreeBSD. ...

Time for fewer optimizations?

[davidwr]

For some types of chips and applications, perhaps having real security means not being able to do fancy optimizations that degrade security.

I wonder how well typical PC operating systems would work if they were re-compiled to not take advantage of optimizations and run on a completely-de-optimized architecture-compatible CPU with buses, memory, chipsets, etc. that were similarly "de-optimized" and had other things in them like less-tightly-packed circuits to prevent certain side-channel attacks (e.g. rowhammer).

Re:Awesome...

[Anonymous Coward]

This was posted to a blog in 2015:

As someone who worked in an Intel Validation group for SOCs until mid-2014, I can tell you, yes, you will see more CPU bugs from Intel than you have in the past.

Why?

In late in 2013 there were meetings with all the validation groups. Head honcho in charge of Validation says something to the effect of: "We need to move faster. Validation is taking much longer than it does for our competition. We need to do whatever we can to reduce those times... we can't live forever in the shadow of the 90's FDIV bug, we need to move on. Our competition is moving much faster than we are." (I'm paraphrasing. )

Many of us were aghast that someone highly placed would suggest we needed to cut corners in validation. That wasn't explicitly said, of course, but that was the implicit message.

Intel vs. the rest of the world

[DrYak]

I thought AMD and ARM cpus were also susceptible to exploits. Is that wrong?

Indeed lots of different CPU manufacturer could be producing CPUs susceptible to spectre vulnerabilities.

But not all CPU are created equal.

There are some key differences :
  - not all CPUs actually do speculative execution. only a couple of ARM core actually do. The huge remaining amount doesn't and thus can't in any way be subjected to Spectre class vulnerabilities.

(Even some of Intel's own core, like some older Atom, or like Xeon Phi GPGPUs don't do speculative execution)

Intel has a different safety vs optimization threshold than most of others:

  - with most other CPU manufacturer, Spectre vulnerabilities boil down to "access memory region to which the process should already have had read access anyway" (see v1 and v4), thus it could be already addressed by safe practice (v1: don't put 3rd-provided JIT code and crucial information in the same process. e.g.: a browser's JIT engine running webpage's scripts and the password manager should not be in the same process) (v4: always clean up your stack before bailing out if it could contain cricital data, or better keep all the critical data in some specific mapped pages), etc.

  - Intel tends to push performance first to the detriment of anything else : some security test coming in too late.

AMD and most ARM won't speculate past memory protection. If a memory region is blocked from access for the process (generally : kernel memory), AMD will check the memory protection and never attempt to access the restricted region to begin with. Whereas Intel CPUs will speculatively access the restricted region and only do the check much latter, by which point the usual Spectre's cache loading side-channel leakage could have happened.
(There are few select ARM which are susceptible to Spectre v3a. Basically the same concept, but regarding system-reserved register - this being RISC architecture, with tons of registers)

AMD and ARM will honor non-maskable interrupt. In today's vulnerability Intel tries to speculatively execute the point past which the system should contect switch the FPU registers (which includes stuff like SSE and AVX registers. i.e.: an attacker could be speculatively peeking into what another process did with these - SIMD operations with SSE/AVX are used in encryption/decryption, so an attacker could occasionnally spot what other process are decrypting/encrypting and whith which keys)

So you end up with vulnerabilities v3 and today's which are Intel exclusive.

Also Intel tends to be a tiny bit more aggressive and/or jumping through some shortcut and/or having way deeper pipeline and longer speculations, in order to shave a few cycles off :
end results :
v2 (Indirect Branch prediction) is currently successfully exploitable on Intel. Though in theory some AMD CPU could do speculative indirect branching, there are no current usable exploits in the wild.
v1 actually works on Intel CPU without even activating the JIT - the speculation is so deep that an bytecode interpreter could speculatively access stuff
v4 works much easier on Intel (deeper pipeline higher chance to manage to read something that wasn't erased from memory yet)
etc.

TL;DR: due to technical choices prioritizing performance, Intel CPU tend to be even more vulnerable.