From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 61752CA9EB7 for ; Wed, 23 Oct 2019 18:21:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4415D21872 for ; Wed, 23 Oct 2019 18:21:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388625AbfJWSVU (ORCPT ); Wed, 23 Oct 2019 14:21:20 -0400 Received: from mga09.intel.com ([134.134.136.24]:4472 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388078AbfJWSVU (ORCPT ); Wed, 23 Oct 2019 14:21:20 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by orsmga102.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Oct 2019 11:21:06 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,221,1569308400"; d="scan'208";a="210120369" Received: from sjchrist-coffee.jf.intel.com (HELO linux.intel.com) ([10.54.74.41]) by orsmga002.jf.intel.com with ESMTP; 23 Oct 2019 11:21:06 -0700 Date: Wed, 23 Oct 2019 11:21:06 -0700 From: Sean Christopherson To: Jim Mattson Cc: kvm@vger.kernel.org, Paolo Bonzini , John Sperbeck Subject: Re: [PATCH] kvm: call kvm_arch_destroy_vm if vm creation fails Message-ID: <20191023182106.GB26295@linux.intel.com> References: <20191023171435.46287-1-jmattson@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191023171435.46287-1-jmattson@google.com> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Wed, Oct 23, 2019 at 10:14:35AM -0700, Jim Mattson wrote: > From: John Sperbeck > > In kvm_create_vm(), if we've successfully called kvm_arch_init_vm(), but > then fail later in the function, we need to call kvm_arch_destroy_vm() > so that it can do any necessary cleanup (like freeing memory). > > Fixes: 44a95dae1d229a ("KVM: x86: Detect and Initialize AVIC support") > Signed-off-by: John Sperbeck > Signed-off-by: Jim Mattson > --- > virt/kvm/kvm_main.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index fd68fbe0a75d2..10ac7ae03677b 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -645,7 +645,7 @@ static struct kvm *kvm_create_vm(unsigned long type) > > r = kvm_arch_init_vm(kvm, type); > if (r) > - goto out_err_no_disable; > + goto out_err_no_arch_destroy_vm; > > r = hardware_enable_all(); > if (r) > @@ -698,10 +698,12 @@ static struct kvm *kvm_create_vm(unsigned long type) > hardware_disable_all(); > out_err_no_disable: > refcount_set(&kvm->users_count, 0); > + kvm_arch_destroy_vm(kvm); Calling destroy_vm() after zeroing the refcount could lead to a refcount underrun (and a WARN with CONFIG_REFCOUNT_FULL=y) if an arch were to do kvm_put_kvm() in destroy_vm() to pair with a kvm_get_kvm() in create_vm(). I doubt any arch actually does that, but it's technically possible since kvm_arch_create_vm() is called with users_count=1. If we wanted to be paranoid, a follow-up patch could change refcount_set() to WARN_ON(!refcount_dec_and_dest()), e.g.: kvm_arch_destroy_vm(kvm); WARN_ON(!refcount_dec_and_dest(&kvm->users_count)); > for (i = 0; i < KVM_NR_BUSES; i++) > kfree(kvm_get_bus(kvm, i)); > for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) > kvm_free_memslots(kvm, __kvm_memslots(kvm, i)); > +out_err_no_arch_destroy_vm: > kvm_arch_free_vm(kvm); > mmdrop(current->mm); > return ERR_PTR(r); > -- > 2.23.0.866.gb869b98d4c-goog >