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=-8.5 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=unavailable 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 DAA1DC4740A for ; Tue, 10 Sep 2019 13:04:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BA50D208E4 for ; Tue, 10 Sep 2019 13:04:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726282AbfIJNEk (ORCPT ); Tue, 10 Sep 2019 09:04:40 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48154 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725916AbfIJNEk (ORCPT ); Tue, 10 Sep 2019 09:04:40 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 58B717DD11; Tue, 10 Sep 2019 13:04:39 +0000 (UTC) Received: from [10.36.118.100] (unknown [10.36.118.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2C3E61001B01; Tue, 10 Sep 2019 13:04:37 +0000 (UTC) Subject: Re: [PATCH] KVM: s390: kvm_s390_vm_start_migration: check dirty_bitmap before using it as target for memset() To: Igor Mammedov , linux-kernel@vger.kernel.org Cc: borntraeger@de.ibm.com, cohuck@redhat.com, frankja@linux.ibm.com, heiko.carstens@de.ibm.com, gor@linux.ibm.com, imbrenda@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org References: <20190910130215.23647-1-imammedo@redhat.com> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190910130215.23647-1-imammedo@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 10 Sep 2019 13:04:39 +0000 (UTC) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 10.09.19 15:02, Igor Mammedov wrote: > If userspace doesn't set KVM_MEM_LOG_DIRTY_PAGES on memslot before calling > kvm_s390_vm_start_migration(), kernel will oops with: > > Unable to handle kernel pointer dereference in virtual kernel address space > Failing address: 0000000000000000 TEID: 0000000000000483 > Fault in home space mode while using kernel ASCE. > AS:0000000002a2000b R2:00000001bff8c00b R3:00000001bff88007 S:00000001bff91000 P:000000000000003d > Oops: 0004 ilc:2 [#1] SMP > ... > Call Trace: > ([<001fffff804ec552>] kvm_s390_vm_set_attr+0x347a/0x3828 [kvm]) > [<001fffff804ecfc0>] kvm_arch_vm_ioctl+0x6c0/0x1998 [kvm] > [<001fffff804b67e4>] kvm_vm_ioctl+0x51c/0x11a8 [kvm] > [<00000000008ba572>] do_vfs_ioctl+0x1d2/0xe58 > [<00000000008bb284>] ksys_ioctl+0x8c/0xb8 > [<00000000008bb2e2>] sys_ioctl+0x32/0x40 > [<000000000175552c>] system_call+0x2b8/0x2d8 > INFO: lockdep is turned off. > Last Breaking-Event-Address: > [<0000000000dbaf60>] __memset+0xc/0xa0 > > due to ms->dirty_bitmap being NULL, which might crash the host. > > Make sure that ms->dirty_bitmap is set before using it or > print a warning and return -ENIVAL otherwise. > > Fixes: afdad61615cc ("KVM: s390: Fix storage attributes migration with memory slots") > Signed-off-by: Igor Mammedov > --- > Cc: stable@vger.kernel.org # v4.19+ > > v2: > - drop WARN() > > arch/s390/kvm/kvm-s390.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c > index f329dcb3f44c..2a40cd3e40b4 100644 > --- a/arch/s390/kvm/kvm-s390.c > +++ b/arch/s390/kvm/kvm-s390.c > @@ -1018,6 +1018,8 @@ static int kvm_s390_vm_start_migration(struct kvm *kvm) > /* mark all the pages in active slots as dirty */ > for (slotnr = 0; slotnr < slots->used_slots; slotnr++) { > ms = slots->memslots + slotnr; > + if (!ms->dirty_bitmap) > + return -EINVAL; > /* > * The second half of the bitmap is only used on x86, > * and would be wasted otherwise, so we put it to good > We properly hold the slots lock, so the bitmap cannot change while in the loop. Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb