Description

In the Linux kernel, the following vulnerability has been resolved: KVM: arm64: Reassign nested_mmus array behind mmu_lock kvm->arch.nested_mmus[] is walked under kvm->mmu_lock, including from the MMU notifier path (kvm_unmap_gfn_range() -> kvm_nested_s2_unmap()), which can run at any time. kvm_vcpu_init_nested() reallocates the array and frees the old buffer while holding only kvm->arch.config_lock, so such a walker can reference the freed array. Allocate the new array outside of mmu_lock, as the allocation can sleep. Under the lock, copy the existing entries, fix up the back pointers and reassign the array. Free the old buffer after dropping the lock, as kvfree() can sleep as well.

References 3

• git.kernel.org https://git.kernel.org/stable/c/4424dbcb06d68e34e51c019a5781a7dc00731971
• git.kernel.org https://git.kernel.org/stable/c/70543358fa08e0f7cebc3447c3b70fe97ad7aaa8
• git.kernel.org https://git.kernel.org/stable/c/918450ad6010df6ecd2efde12a1409e011da22d6

Remediation