Theo de Raadt on the Intel Core 2 Jun 27, 2007

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openBSD developer Theo de Raadt had this to say in a legendary message to the openbsd-misc e-mail list on Jun 27, 2007:

"Various developers are busy implimenting workarounds for serious bugs in Intel's Core 2 cpu.

These processors are buggy as hell, and some of these bugs don't just cause development/debugging problems, but will *ASSUREDLY* be exploitable from userland code.

As is typical, BIOS vendors will be very late providing workarounds / fixes for these processors bugs. Some bugs are unfixable and cannot be worked around. Intel only provides detailed fixes to BIOS vendors and large operating system groups. Open Source operating systems are largely left in the cold.

Full (current) errata from Intel:

  • We bet there are many more errata not yet announced -- every month this file gets larger.
  • Intel understates the impact of these erraata very significantly. Almost all operating systems will run into these bugs.
  • Basically the MMU simply does not operate as specified/implemented in previous generations of x86 hardware. It is not just buggy, but Intel has gone further and defined "new ways to handle page tables" (see page 58).
  • Some of these bugs are along the lines of "buffer overflow"; where a write-protect or non-execute bit for a page table entry is ignored. Others are floating point instruction non-coherencies, or memory corruptions -- outside of the range of permitted writing for the process -- running common instruction sequences.
  • All of this is just unbelievable to many of us.

An easier summary document for some people to read: [link dead by now]

Note that some errata like AI65, AI79, AI43, AI39, AI90, AI99 scare the hell out of us. Some of these are things that cannot be fixed in running code, and some are things that every operating system will do until about mid-2008, because that is how the MMU has always been managed on all generations of Intel/AMD/whoever-else hardware. Now Intel is telling people to manage the MMU's TLB flushes in a new and different way. Yet even if we do so, some of the errata listed are unaffected by doing so.

As I said before, hiding in this list are 20-30 bugs that cannot be worked around by operating systems, and will be potentially exploitable. I would bet a lot of money that at least 2-3 of them are.

For instance, AI90 is exploitable on some operating systems (but not OpenBSD running default binaries).

At this time, I cannot recommend purchase of any machines based on the Intel Core 2 until these issues are dealt with (which I suspect will take more than a year). Intel must be come more transparent.

(While here, I would like to say that AMD is becoming less helpful day by day towards open source operating systems too, perhaps because their serious errata lists are growing rapidly too)."

Theo de Raadt on the Intel Core 2 Jun 27, 2007