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 1655BC43613 for ; Fri, 21 Jun 2019 14:00:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB11F2075E for ; Fri, 21 Jun 2019 14:00:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726097AbfFUOA6 (ORCPT ); Fri, 21 Jun 2019 10:00:58 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:48418 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725985AbfFUOA6 (ORCPT ); Fri, 21 Jun 2019 10:00:58 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5LDxl2E074616 for ; Fri, 21 Jun 2019 10:00:56 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2t900h1ud5-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 21 Jun 2019 10:00:55 -0400 Received: from localhost by e06smtp02.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Fri, 21 Jun 2019 15:00:39 +0100 Received: from b06avi18878370.portsmouth.uk.ibm.com (9.149.26.194) by e06smtp02.uk.ibm.com (192.168.101.132) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 21 Jun 2019 15:00:36 +0100 Received: from d06av22.portsmouth.uk.ibm.com (d06av22.portsmouth.uk.ibm.com [9.149.105.58]) by b06avi18878370.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x5LE0ZnC25100596 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2019 14:00:35 GMT Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 788CD4C06A; Fri, 21 Jun 2019 14:00:34 +0000 (GMT) Received: from d06av22.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 422434C07E; Fri, 21 Jun 2019 14:00:34 +0000 (GMT) Received: from oc2783563651 (unknown [9.152.224.137]) by d06av22.portsmouth.uk.ibm.com (Postfix) with ESMTP; Fri, 21 Jun 2019 14:00:34 +0000 (GMT) Date: Fri, 21 Jun 2019 16:00:32 +0200 From: Halil Pasic To: Farhan Ali Cc: cohuck@redhat.com, farman@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org Subject: Re: [RFC v1 1/1] vfio-ccw: Don't call cp_free if we are processing a channel program In-Reply-To: <46dc0cbdcb8a414d70b7807fceb1cca6229408d5.1561055076.git.alifm@linux.ibm.com> References: <46dc0cbdcb8a414d70b7807fceb1cca6229408d5.1561055076.git.alifm@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.31; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 x-cbid: 19062114-0008-0000-0000-000002F5DAEB X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19062114-0009-0000-0000-00002262FFC6 Message-Id: <20190621160032.1bd0c15f.pasic@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-06-21_10:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=2 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=921 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906210117 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, 20 Jun 2019 17:07:09 -0400 Farhan Ali wrote: > There is a small window where it's possible that an interrupt can > arrive and can call cp_free, while we are still processing a channel > program (i.e allocating memory, pinnging pages, translating > addresses etc). This can lead to allocating and freeing at the same > time and can cause memory corruption. > > Let's not call cp_free if we are currently processing a channel program. > > Signed-off-by: Farhan Ali > --- > > I have been running my test overnight with this patch and I haven't > seen the stack traces that I mentioned about earlier. I would like > to get some reviews on this and also if this is the right thing to > do? > > Thanks > Farhan > > 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 66a66ac..61ece3f 100644 > --- a/drivers/s390/cio/vfio_ccw_drv.c > +++ b/drivers/s390/cio/vfio_ccw_drv.c > @@ -88,7 +88,7 @@ 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_PROCESSING) How is access to private->state correctly synchronized? And don't we expect private->state == VFIO_CCW_STATE_CP_PENDING in case the cp was submitted successfully with a ssch() and is done now (one way or the other)? Does this have something to do with 71189f2 "vfio-ccw: make it safe to access channel programs" (Cornelia Huck, 2019-01-21)? Regards, Halil > cp_free(&private->cp); > } > mutex_lock(&private->io_mutex);