Executive brief
The Linux kernel's SEV-guest secure enclave code performed encryption operations directly on unencrypted shared memory, allowing the hypervisor host to read plaintext messages and modify data in transit. This undermines the confidentiality and integrity protections that secure enclaves are designed to provide. The fix adds intermediate buffering in protected memory to prevent the host from accessing or tampering with message contents.
Technical details
The vulnerability is a cryptographic implementation flaw in the SEV-guest driver (virt/coco/sev-guest). The encryption and decryption algorithms read and write directly to guest-host shared memory pages without first copying data to protected memory, allowing the host hypervisor to observe plaintext message content and modify it before/after cryptographic operations. The attack is network-adjacent (requires host-level access) and affects any system relying on AMD SEV-SNP secure execution. The fix introduces double-buffering: messages are now copied from unencrypted shared memory to encrypted kernel buffers before cryptographic processing, and copied back only after complete encryption, preventing host observation or tampering.
Affected products
- Linux Linux kernel before fix commit 965006103a14703cc42043bbf9b5e0cdf7a468ad
Timeline
- 2023-03: disclosed: Fix commit authored by Dionna Glaze
- 2023-05-11: patched: Integrated into stable kernel branches by Greg Kroah-Hartman