CVE-2026-46147: KVM: arm64: Fix pin leak and publication ordering in __pkvm_init_vcpu()
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Fix pin leak and publication ordering in pkvminitvcpu()
Two bugs exist in the vCPU initialisation path:
1. If a check fails after hyppinsharedmem() succeeds, the cleanup path jumps to 'unlock' without calling unpinhostvcpu() or unpinhostsvestate(), permanently leaking pin references on the host vCPU and SVE state pages.
Extract a registerhypvcpu() helper that performs the checks and the store. When registerhypvcpu() returns an error, call unpinhostvcpu() and unpinhostsvestate() inline before falling through to the existing 'unlock' label.
2. registerhypvcpu() publishes the new vCPU pointer into 'hypvm->vcpus[]' with a bare store, allowing a concurrent caller of pkvmloadhypvcpu() to observe a partially initialised vCPU object.
Ensure the store uses smpstorerelease() and the load uses smploadacquire(). While 'vmtablelock' currently serialises the store and the load, these barriers ensure the reader sees the fully initialised 'hypvcpu' object even if there were a lockless path or if the lock's own ordering guarantees were insufficient for nested object initialization.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
Update __pkvm_init_vcpu() so publication of the vCPU pointer in hyp_vm->vcpus[] uses smp_store_release() and pkvm_load_hyp_vcpu() uses smp_load_acquire(); ensure failure paths after hyp_pin_shared_mem() call unpin_host_vcpu() and unpin_host_sve_state() before reaching the existing unlock label.
Event History
Frequently Asked Questions
What access does an attacker need to exploit this issue?
The CVSS vector indicates local access with low privileges is required, and no user interaction is needed. The affected code is in the KVM arm64 protected-KVM vCPU initialization path.
What is the expected impact if the vulnerable path is triggered?
Failed initialization after shared-memory pinning can permanently leak pin references for host vCPU and SVE-state pages. A concurrent vCPU load can also observe a partially initialized vCPU object; the CVSS assessment rates availability impact as high, with no confidentiality or integrity impact.