In the Linux kernel, the following vulnerability has been resolved: crypto: ccp - Do not...

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