LVI Attack Hits Intel SGX - Defeats Existing Mitigations, More Performance Hits

Load Value Injection (LVI) is being disclosed today as a new class of transient-execution attacks and the researchers claim can defeat all existing mitigations around Meltdown, Foreshadow, Zombieload, RIDL and Fallout. The researchers say LVI can affect virtually any access to memory and compiler-based mitigations can be expensive.

LVI combines Spectre-style code gadgets with Meltdown-type illegal data flows to bypass existing defenses and allow injecting data into a victim's transient execution. LVI was discovered in April of 2019 while today the researchers and Intel are making a coordinated disclosure. The initial discovery was made again by university researchers but Bitdefender ended up also discovering the same vulnerability.

It is important to note that LVI appears to be predominantly impact Intel SGX and Icelake's hardware mitigations do protect against this vulnerability while other partially mitigated Intel CPUs are only partially vulnerable.

LVI mitigations amount to inserting lfence barriers before every vulnerable load instruction. The researchers also believe that certain instructions need to be blacklisted. The researchers found the prototype compiler-based mitigations have an Intel SGX performance hit of 2x to 19x but the actual real-world impact may differ. Once there are patches available, I'll certainly fire up some real-world benchmarks.

More details on this new attack vector at LVIattack.eu. Intel also published an extensive deep dive on LVI and will be releasing an updated SGX SDK to help with mitigations.