From patchwork Thu Mar 23 17:24:19 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Hildenbrand X-Patchwork-Id: 9641671 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id CB5E5602CA for ; Thu, 23 Mar 2017 17:24:39 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B5C1A25D99 for ; Thu, 23 Mar 2017 17:24:39 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id AA93B2841E; Thu, 23 Mar 2017 17:24:39 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 3862525D99 for ; Thu, 23 Mar 2017 17:24:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756466AbdCWRY2 (ORCPT ); Thu, 23 Mar 2017 13:24:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:60026 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751979AbdCWRY1 (ORCPT ); Thu, 23 Mar 2017 13:24:27 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id B091663319; Thu, 23 Mar 2017 17:24:26 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com B091663319 Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx10.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=david@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com B091663319 Received: from t460s.redhat.com (ovpn-116-209.ams2.redhat.com [10.36.116.209]) by smtp.corp.redhat.com (Postfix) with ESMTP id 7D3F617564; Thu, 23 Mar 2017 17:24:21 +0000 (UTC) From: David Hildenbrand To: kvm@vger.kernel.org Cc: Paolo Bonzini , rkrcmar@redhat.com, Dmitry Vyukov , Marcelo Tosatti , stable@vger.kernel.org, LKML , david@redhat.com, Cornelia Huck Subject: [PATCH v2] KVM: kvm_io_bus_unregister_dev() should never fail Date: Thu, 23 Mar 2017 18:24:19 +0100 Message-Id: <20170323172419.21435-1-david@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 23 Mar 2017 17:24:26 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP No caller currently checks the return value of kvm_io_bus_unregister_dev(). This is evil, as all callers silently go on freeing their device. A stale reference will remain in the io_bus, getting at least used again, when the iobus gets teared down on kvm_destroy_vm() - leading to use after free errors. There is nothing the callers could do, except retrying over and over again. So let's simply remove the bus altogether, print an error and make sure no one can access this broken bus again (returning -ENOMEM on any attempt to access it). Fixes: e93f8a0f821e ("KVM: convert io_bus to SRCU") Cc: stable@vger.kernel.org # 3.4+ Reported-by: Dmitry Vyukov Signed-off-by: David Hildenbrand Reviewed-by: Cornelia Huck --- Based on kvm/queue, where we just got 2a108a4e7c1 ("KVM: x86: clear bus pointer when destroyed"), which added a check we need here. v1 -> v2: - added a check in kvm_destroy_vm() - added a check in virt/kvm/eventfd.c Using 'git grep -C 4 "kvm->buses"' should help to find all users. The other user in virt/kvm/eventfd.c should be fine. --- include/linux/kvm_host.h | 4 ++-- virt/kvm/eventfd.c | 3 ++- virt/kvm/kvm_main.c | 42 +++++++++++++++++++++++++----------------- 3 files changed, 29 insertions(+), 20 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 2c14ad9..d025074 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -162,8 +162,8 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, int len, void *val); int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, int len, struct kvm_io_device *dev); -int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, - struct kvm_io_device *dev); +void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, + struct kvm_io_device *dev); struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr); diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c index a29786d..4d28a9d 100644 --- a/virt/kvm/eventfd.c +++ b/virt/kvm/eventfd.c @@ -870,7 +870,8 @@ kvm_deassign_ioeventfd_idx(struct kvm *kvm, enum kvm_bus bus_idx, continue; kvm_io_bus_unregister_dev(kvm, bus_idx, &p->dev); - kvm->buses[bus_idx]->ioeventfd_count--; + if (kvm->buses[bus_idx]) + kvm->buses[bus_idx]->ioeventfd_count--; ioeventfd_release(p); ret = 0; break; diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 7445566..ef1aa7f 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -728,7 +728,8 @@ static void kvm_destroy_vm(struct kvm *kvm) spin_unlock(&kvm_lock); kvm_free_irq_routing(kvm); for (i = 0; i < KVM_NR_BUSES; i++) { - kvm_io_bus_destroy(kvm->buses[i]); + if (kvm->buses[i]) + kvm_io_bus_destroy(kvm->buses[i]); kvm->buses[i] = NULL; } kvm_coalesced_mmio_free(kvm); @@ -3476,6 +3477,8 @@ int kvm_io_bus_write(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, }; bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu); + if (!bus) + return -ENOMEM; r = __kvm_io_bus_write(vcpu, bus, &range, val); return r < 0 ? r : 0; } @@ -3493,6 +3496,8 @@ int kvm_io_bus_write_cookie(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, }; bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu); + if (!bus) + return -ENOMEM; /* First try the device referenced by cookie. */ if ((cookie >= 0) && (cookie < bus->dev_count) && @@ -3543,6 +3548,8 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, }; bus = srcu_dereference(vcpu->kvm->buses[bus_idx], &vcpu->kvm->srcu); + if (!bus) + return -ENOMEM; r = __kvm_io_bus_read(vcpu, bus, &range, val); return r < 0 ? r : 0; } @@ -3555,6 +3562,9 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, struct kvm_io_bus *new_bus, *bus; bus = kvm->buses[bus_idx]; + if (!bus) + return -ENOMEM; + /* exclude ioeventfd which is limited by maximum fd */ if (bus->dev_count - bus->ioeventfd_count > NR_IOBUS_DEVS - 1) return -ENOSPC; @@ -3574,45 +3584,41 @@ int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, } /* Caller must hold slots_lock. */ -int kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, - struct kvm_io_device *dev) +void kvm_io_bus_unregister_dev(struct kvm *kvm, enum kvm_bus bus_idx, + struct kvm_io_device *dev) { - int i, r; + int i; struct kvm_io_bus *new_bus, *bus; bus = kvm->buses[bus_idx]; - - /* - * It's possible the bus being released before hand. If so, - * we're done here. - */ if (!bus) - return 0; + return; - r = -ENOENT; for (i = 0; i < bus->dev_count; i++) if (bus->range[i].dev == dev) { - r = 0; break; } - if (r) - return r; + if (i == bus->dev_count) + return; new_bus = kmalloc(sizeof(*bus) + ((bus->dev_count - 1) * sizeof(struct kvm_io_range)), GFP_KERNEL); - if (!new_bus) - return -ENOMEM; + if (!new_bus) { + pr_err("kvm: failed to shrink bus, removing it completely\n"); + goto broken; + } memcpy(new_bus, bus, sizeof(*bus) + i * sizeof(struct kvm_io_range)); new_bus->dev_count--; memcpy(new_bus->range + i, bus->range + i + 1, (new_bus->dev_count - i) * sizeof(struct kvm_io_range)); +broken: rcu_assign_pointer(kvm->buses[bus_idx], new_bus); synchronize_srcu_expedited(&kvm->srcu); kfree(bus); - return r; + return; } struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx, @@ -3625,6 +3631,8 @@ struct kvm_io_device *kvm_io_bus_get_dev(struct kvm *kvm, enum kvm_bus bus_idx, srcu_idx = srcu_read_lock(&kvm->srcu); bus = srcu_dereference(kvm->buses[bus_idx], &kvm->srcu); + if (!bus) + goto out_unlock; dev_idx = kvm_io_bus_get_first_dev(bus, addr, 1); if (dev_idx < 0)