From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alex Williamson Subject: [PATCH 01/10] kvm: Restrict non-existing slot state transitions Date: Thu, 06 Dec 2012 15:20:20 -0700 Message-ID: <20121206222019.24968.92027.stgit@bling.home> References: <20121206214722.24968.6043.stgit@bling.home> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org To: mtosatti@redhat.com, gleb@redhat.com Return-path: In-Reply-To: <20121206214722.24968.6043.stgit@bling.home> Sender: linux-kernel-owner@vger.kernel.org List-Id: kvm.vger.kernel.org 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. Signed-off-by: Alex Williamson --- virt/kvm/kvm_main.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6e8fa7e..e426704 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -753,10 +753,15 @@ 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; @@ -775,7 +780,7 @@ 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;