Ubuntu 24.04 SEV-SNP disk writes leak via DMA bounce buffers

The author demonstrates that confidential virtual machines using memory encryption technologies like AMD SEV-SNP still leak disk writes to the hypervisor because the Linux kernel copies block I/O data into shared RAM bounce buffers as plaintext. To prevent the host from reading disk contents, the author explains how to encrypt data inside the guest using dm-crypt and LUKS2 before it reaches shared memory. Open article →