A couple of days ago we reported the news concerning the discovery of one dangerous vulnerability identified on processors based on Zen 3 microarchitecture caused by the called technology Predictive Store Forwarding (PSF), initially intended for improve performance by predicting the relationships between data loading and storage. Unfortunately, in a very similar way to what happened in the past with Spectre, which involved several generations of different processor architectures, any erroneous speculation could allow malicious individuals to gain possession of sensitive information through targeted attacks.
AMD has released a whitepaper in recent days in which it explained more precisely all the details concerning the problem, promising that it would distribute new patches for the Linux kernel in order to mitigate the potential security risk of the Predictive Store Forwarding (PSF) function. Apparently, the company has kept its promise, as Phoronix colleagues have identified five patches that allow users to disable that feature if desired.
Recall that software that uses “sandboxing” are more susceptible to exploit, which is why AMD has offered users the ability to disable Predictive Store Forwarding. As noted by Phoronix, Predictive Store Forwarding is enabled by default on the patched Linux kernel as well. It can be deactivated in two ways: through the Specter v4 mitigation control or by inserting the “nopsfd” parameter between the start ones. Fortunately, it appears that deactivating PSF does not lead to substantial decreases in performance, as verified by the tests conducted by Phoronix.
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