From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [patch] kvm: make cr3 loading more robust Date: Wed, 03 Jan 2007 10:29:16 +0200 Message-ID: <459B695C.5090004@qumranet.com> References: <20070103021057.GA11316@elte.hu> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel Return-path: To: Ingo Molnar In-Reply-To: <20070103021057.GA11316-X9Un+BFzKDI@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Ingo Molnar wrote: > From: Ingo Molnar > Subject: [patch] kvm: make cr3 loading more robust > > rmap_write_protect() has a BUG_ON() if a physical address is not found > the the memslot. But this is a possible scenario if a buggy guest OS > loads an invalid or corrupted cr3 value. So exit more gracefully. > > I think a better solution is to detect the invalid cr3 in new_cr3(). That way the entire chain of error returns is avoided. > [ Avi: this patch needs kvm_mmu_get_page() NULL return to not be ignored > by mmu_alloc_roots()/nonpaging_init_context()/paging_new_cr3()/etc. > and passed further down - i assume you are working on those > issues already, or should i fix those too? ] > kvm_mmu_get_page() cannot return NULL (before this patch), as we ensure there are free pages before entry to page_fault. > Signed-off-by: Ingo Molnar > > Index: linux/drivers/kvm/mmu.c > =================================================================== > --- linux.orig/drivers/kvm/mmu.c > +++ linux/drivers/kvm/mmu.c > @@ -378,7 +378,7 @@ static void rmap_remove(struct kvm_vcpu > } > } > > -static void rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn) > +static int rmap_write_protect(struct kvm_vcpu *vcpu, u64 gfn) > { > struct kvm *kvm = vcpu->kvm; > struct page *page; > @@ -387,7 +387,8 @@ static void rmap_write_protect(struct kv > u64 *spte; > > slot = gfn_to_memslot(kvm, gfn); > - BUG_ON(!slot); > + if (!slot) > + return -1; > page = gfn_to_page(slot, gfn); > > while (page->private) { > @@ -407,6 +408,7 @@ static void rmap_write_protect(struct kv > kvm_arch_ops->tlb_flush(vcpu); > *spte &= ~(u64)PT_WRITABLE_MASK; > } > + return 0; > } > > static int is_empty_shadow_page(hpa_t page_hpa) > @@ -592,12 +594,17 @@ static struct kvm_mmu_page *kvm_mmu_get_ > page = kvm_mmu_alloc_page(vcpu, parent_pte); > if (!page) > return page; > + if (!metaphysical) { > + if (rmap_write_protect(vcpu, gfn) < 0) { > + kvm_mmu_free_page(vcpu, page->page_hpa); > + return NULL; > + } > + } > pgprintk("%s: adding gfn %lx role %x\n", __FUNCTION__, gfn, role.word); > page->gfn = gfn; > page->role = role; > hlist_add_head(&page->hash_link, bucket); > - if (!metaphysical) > - rmap_write_protect(vcpu, gfn); > + > return page; > } > > -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV