Jue Wang

**Name of the Vulnerable Software and Affected Versions** Linux kernel (affected versions not specified) **Description** A rare kernel panic scenario can occur due to an erratum on fast string copy instructions in the Linux kernel. This issue happens when an uncorrected error is present in the first cache line of a page, and the kernel executes page copy from the page immediately before that page. The fast string copy instructions could consume an uncorrectable memory error and raise a Machine Check Exception (MCE). This erratum is confirmed by Intel to only apply to Skylake, Cascade Lake, and Cooper Lake generations. **Recommendations** To mitigate this issue, consider disabling fast string copy by clearing bit 0 of MSR IA32 MISC ENABLE, although this may result in a permanent performance impact. Alternatively, the kernel can be modified to directly return from the MCE handler, which will prevent the kernel panic but may still result in performance degradation due to the disabling of fast string copy on the affected hyper thread. At the moment, there is no information about a newer version that contains a fix for this vulnerability.