Meltdown and Spectre
maddog's Doghouse
A serious security problem requires your attention.
I was lying in my bed in the early morning of January 3rd, 2018 when a tweet woke me from my sleep; not a tweet from a bird (nor from the president of the United States), but a tweet from a security researcher discussing two rather bad hardware issues with a large number of CPU chips.
These issues, now known as "Meltdown" and "Spectre," have been rocking the computing world for the past couple of days. Unlike many other security exploits, these are not really "fixable" by a simple software patch, are not operating-system specific, and cannot be avoided by telling your mother not to post her password on her computer screen.
Both have to do with modern hardware architecture and an issue called "out-of-order instruction execution," used to speed up the processor. Sometimes this feature is used to fetch instructions on both sides of a branch (both the "true" and the "false" side), so as soon as the condition is known, the instructions are ready to execute. Access to this "pre-fetched" data could allow a carefully crafted user-level program to access kernel memory, and once that happens, any data on the machine is vulnerable to be read, including passwords, security certificates, and so forth.
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