crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG)

Overview

In the Linux kernel, the following vulnerability has been resolved:

crypto: ccp - Do not initialize SNP for ioctl(SNP_CONFIG)

Sashiko notes:

if SEV initialization fails and KVM is actively running normal VMs, could a userspace process trigger this code path via /dev/sev ioctls (e.g., SEV_PDH_GEN) and zero out MSR_VM_HSAVE_PA globally? Would the next VMRUN execution for an active VM trigger a general protection fault and crash the host?

Refuse to re-try initialization if SNP is not already initialized for SNP_CONFIG.

This is technically an ABI break: before if SNP initialization failed it could be transparently retriggered by this ioctl, and if no VMs were running, everything worked fine. Hopefully this is enough of a corner case that nobody will notice, but someone does, there are a few options:

• do something like symbol_get() for kvm and refuse to initialize if KVM is loaded
• check each cpu's HSAVE_PA for non-zero data before re-initializing
• once initialization has failed, continue to refuse to initialize until the ccp module is unloaded

Affected

• Linux >= 1c3506ea8599a3ad1b9aae5cbd573134f8d18db7 < 345a6e869b33687e9268044bcaeeefd7c61da675
• Linux >= ceac7fb89e8da465aec3ac3c20477f912f5c3a6c < 441ea32cf2755a0dc593557056b00b7caa0651f5
• Linux >= ceac7fb89e8da465aec3ac3c20477f912f5c3a6c < 20f548cdac94860a164e5ebba4f7e4a01051cb06
• Linux >= ceac7fb89e8da465aec3ac3c20477f912f5c3a6c < 08f0e65e784c4b20e6e620dd4f68d8636073a3d2
• Linux >= 6.12.75 < 6.12.97
• Linux 6.16

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.