IOS: A Low Cost Defense to Mitigate Meltdown and Spectre Like Attacks

The Meltdown and Spectre attacks brings severe security issues to a wide range of modern processors. The Meltdown steals sensitive information in the kernel memory space by utilizing the nature of out-of-order execution and the Spectre exploits the speculative execution to access the secret data. Both attacks transmit the secrets via the cache side-channels. Although software patches have been applied to protect the processors from the Meltdown and Spectre attacks, the countermeasure also introduces huge performance degradation and close the door to the benefit of out-of-order and speculative execution. Customizing a hardware-based solution can be more performance friendly and also conserve the bonus the out-of-order and speculative execution. In this paper, we proposed a hardware-based mitigation technique named Invalidation on Squash (IOS) which is able to close the cache covert channel and stops Meltdown and Spectre from exposing the secrets to the adversary. To simplify the additional defense logic and minimize the hardware overhead, IOS targets the squashed load instructions and invalidates the corresponding cache lines introduced by these squashed loads. Compared to the existing Meltdown and Spectre Countermeasures, IOS incurs only negligible hardware overhead by taking the advantage of the simple invalidation logic.