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 <gleb@redhat.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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@ -758,10 +758,15 @@ int __kvm_set_memory_region(struct kvm *kvm,
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new.npages = npages;
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new.npages = npages;
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new.flags = mem->flags;
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new.flags = mem->flags;
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/* Disallow changing a memory slot's size. */
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/*
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* Disallow changing a memory slot's size or changing anything about
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* zero sized slots that doesn't involve making them non-zero.
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*/
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r = -EINVAL;
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r = -EINVAL;
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if (npages && old.npages && npages != old.npages)
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if (npages && old.npages && npages != old.npages)
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goto out_free;
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goto out_free;
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if (!npages && !old.npages)
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goto out_free;
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/* Check for overlaps */
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/* Check for overlaps */
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r = -EEXIST;
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r = -EEXIST;
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@ -780,7 +785,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
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r = -ENOMEM;
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r = -ENOMEM;
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/* Allocate if a slot is being created */
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/* Allocate if a slot is being created */
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if (npages && !old.npages) {
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if (!old.npages) {
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new.user_alloc = user_alloc;
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new.user_alloc = user_alloc;
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new.userspace_addr = mem->userspace_addr;
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new.userspace_addr = mem->userspace_addr;
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