From f0736cf0550b349a5d5a374d65ca0488cc2eee40 Mon Sep 17 00:00:00 2001 From: Alex Williamson Date: Mon, 10 Dec 2012 10:32:45 -0700 Subject: KVM: Restrict non-existing slot state transitions The API documentation states: When changing an existing slot, it may be moved in the guest physical memory space, or its flags may be modified. An "existing slot" requires a non-zero npages (memory_size). The only transition we should therefore allow for a non-existing slot should be to create the slot, which includes setting a non-zero memory_size. We currently allow calls to modify non-existing slots, which is pointless, confusing, and possibly wrong. With this we know that the invalidation path of __kvm_set_memory_region is always for a delete or move and never for adding a zero size slot. Reviewed-by: Gleb Natapov Signed-off-by: Alex Williamson Signed-off-by: Marcelo Tosatti diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 1cd693a..3caf816 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -758,10 +758,15 @@ int __kvm_set_memory_region(struct kvm *kvm, new.npages = npages; new.flags = mem->flags; - /* Disallow changing a memory slot's size. */ + /* + * Disallow changing a memory slot's size or changing anything about + * zero sized slots that doesn't involve making them non-zero. + */ r = -EINVAL; if (npages && old.npages && npages != old.npages) goto out_free; + if (!npages && !old.npages) + goto out_free; /* Check for overlaps */ r = -EEXIST; @@ -780,7 +785,7 @@ int __kvm_set_memory_region(struct kvm *kvm, r = -ENOMEM; /* Allocate if a slot is being created */ - if (npages && !old.npages) { + if (!old.npages) { new.user_alloc = user_alloc; new.userspace_addr = mem->userspace_addr; -- cgit v0.10.2