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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 AEE00C606B0 for ; Tue, 9 Jul 2019 10:16:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 878E620645 for ; Tue, 9 Jul 2019 10:16:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726232AbfGIKQT (ORCPT ); Tue, 9 Jul 2019 06:16:19 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58916 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725989AbfGIKQS (ORCPT ); Tue, 9 Jul 2019 06:16:18 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8DE61309178C; Tue, 9 Jul 2019 10:16:18 +0000 (UTC) Received: from gondolin (unknown [10.40.205.62]) by smtp.corp.redhat.com (Postfix) with ESMTP id 183A457985; Tue, 9 Jul 2019 10:16:16 +0000 (UTC) Date: Tue, 9 Jul 2019 12:16:13 +0200 From: Cornelia Huck To: Farhan Ali Cc: farman@linux.ibm.com, pasic@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC v2 4/5] vfio-ccw: Don't call cp_free if we are processing a channel program Message-ID: <20190709121613.6a3554fa.cohuck@redhat.com> In-Reply-To: <1405df8415d3bff446c22753d0e9b91ff246eb0f.1562616169.git.alifm@linux.ibm.com> References: <1405df8415d3bff446c22753d0e9b91ff246eb0f.1562616169.git.alifm@linux.ibm.com> Organization: Red Hat GmbH MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Tue, 09 Jul 2019 10:16:18 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, 8 Jul 2019 16:10:37 -0400 Farhan Ali wrote: > There is a small window where it's possible that we could be working > on an interrupt (queued in the workqueue) and setting up a channel > program (i.e allocating memory, pinning pages, translating address). > This can lead to allocating and freeing the channel program at the > same time and can cause memory corruption. > > Let's not call cp_free if we are currently processing a channel program. > The only way we know for sure that we don't have a thread setting > up a channel program is when the state is set to VFIO_CCW_STATE_CP_PENDING. Can we pinpoint a commit that introduced this bug, or has it been there since the beginning? > > Signed-off-by: Farhan Ali > --- > drivers/s390/cio/vfio_ccw_drv.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/s390/cio/vfio_ccw_drv.c b/drivers/s390/cio/vfio_ccw_drv.c > index 4e3a903..0357165 100644 > --- a/drivers/s390/cio/vfio_ccw_drv.c > +++ b/drivers/s390/cio/vfio_ccw_drv.c > @@ -92,7 +92,7 @@ static void vfio_ccw_sch_io_todo(struct work_struct *work) > (SCSW_ACTL_DEVACT | SCSW_ACTL_SCHACT)); > if (scsw_is_solicited(&irb->scsw)) { > cp_update_scsw(&private->cp, &irb->scsw); > - if (is_final) > + if (is_final && private->state == VFIO_CCW_STATE_CP_PENDING) > cp_free(&private->cp); > } > mutex_lock(&private->io_mutex); Reviewed-by: Cornelia Huck