Thursday, March 16th 2017
AMD Ryzen Machine Crashes to a Sequence of FMA3 Instructions
An AMD Ryzen 7-1800X powered machine was found to be crashing upon execution of a very specific set of FMA3 instructions by Flops version 2, a simple open-source CPU benchmark by Alexander "Mystical" Yee. An important point to note here is that this little known benchmark has been tailored by its developer to be highly specific to the CPU micro-architecture, with separate binaries for each major x64 architecture (eg: Bulldozer, Sandy Bridge, Haswell, Skylake, etc.), and as such the GitHub repository does not have a "Zen" specific binary.
Members of the HWBot forums found that Ryzen powered machines crash on running the Haswell-specific binary, at "Single-Precision - 128-bit FMA3 - Fused Multiply Add." The Haswell-specific binary (along with, we imagine, Skylake), adds support for the FMA3 instruction-set, which Ryzen supports, and which lends some importance to the discovery of this bug. What also makes this important is because a simple application, running at user privileges (i.e. lacking special super-user/admin privileges), has the ability to crash the machine. Such a code could even be executed through virtual machines, and poses a security issue, with implications for AMD's upcoming "Naples" enterprise processor launch.
Members of the HWBot forums found that Ryzen powered machines crash on running the Haswell-specific binary, at "Single-Precision - 128-bit FMA3 - Fused Multiply Add." The Haswell-specific binary (along with, we imagine, Skylake), adds support for the FMA3 instruction-set, which Ryzen supports, and which lends some importance to the discovery of this bug. What also makes this important is because a simple application, running at user privileges (i.e. lacking special super-user/admin privileges), has the ability to crash the machine. Such a code could even be executed through virtual machines, and poses a security issue, with implications for AMD's upcoming "Naples" enterprise processor launch.
62 Comments on AMD Ryzen Machine Crashes to a Sequence of FMA3 Instructions
Morale of story, the specific open source bench, as alluded to in OP hasn't got the Zen instruction set yet....
This is news because an unprivileged application can take down a machine (and is hence a security hole). Would a company like Barclay's put its client live database on a "Naples" machine now?
Hopefully a BIOS or windows security update can fix this one before it goes bad.
@Mussels, everything can be crashed. Especially on such esoteric and unique program with a specific instruction set.
I'm not saying it's not an issue but it's very specific and very minor. Every major operating system has almost weekly vulnerability exposed.
Now we have Intel fan boys on wccftech spreading rumors of Ryzen being a design flaw due to this article lol, ridiculous.
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As for this case, it was said that OCed processors didn't had any problem and probably AMD will only have to throw a little more current in the part of the processor doing the FMA3 job - or however someone can describe it better - to keep them stable.
FWIW, I doubt this is something that can't be simply fixed with a microcode update.
After all, every CPU ends up with hundreds of errata, some a lot scarier than simple DoS such as this one.
This news isn't a big deal...