AMD confirms minor bug in some of its CPUs

Posted on Tuesday, March 06 2012 @ 14:31 CET by Thomas De Maesschalck

AMD has confirmed a report from researcher Matt Dillon of DragonFly BSD that there's a bug in some AMD processor families. Dillon discovered that running a very specific sequence of consecutive back-to-back pops and (near) return instructions can create a condition where the process incorrectly updates the stack pointer, leading to a segmentation fault.

The bug was reproduced on an Opteron 6168 and Phenom II X4 820 processor, but its unknown how many other chips are affected. It seems it's just ordinary errata, the bug is quite specific, it does not lead to data corruption and it's hard to reproduce:

We exchanged a few emails to try to come up with a good test case. Owing to the difficulty of reproducing the bug I constructed a fully bootable DFly operating system & test case USB image and verified that the bug was present on my test box using that image. AMD was then able to reproduce the bug using that image on their own machines. Over the last few months they have been working through the possibilities and today emailed me the confirmation that it was, indeed, a cpu bug.

About the Author

Thomas De Maesschalck

Thomas has been messing with computer since early childhood and firmly believes the Internet is the best thing since sliced bread. Enjoys playing with new tech, is fascinated by science, and passionate about financial markets. When not behind a computer, he can be found with running shoes on or lifting heavy weights in the weight room.

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