Intel processors with Linear Address Masking (LAM): SLAM: Linear Address Masking, a feature intended to let software

Impact

SLAM: Linear Address Masking, a feature intended to let software store metadata in unused address bits, makes previously impractical Spectre gadgets exploitable by widening the set of usable pointer-chasing gadgets - so a performance and usability feature became a security regression. Notable as a case where the mitigation was to ship the hardware feature disabled by default in Linux.

Who can reach it

Local unprivileged code on a host with LAM enabled.

What to do

Linux disables LAM by default in response; keep it disabled unless you have a specific requirement and have assessed the tradeoff. Kernel-level configuration - a kernel update and reboot, no microcode or BIOS. Verify LAM state on your nodes rather than assuming the default held through a kernel upgrade.

References