From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:63302 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725985AbfFUOAv (ORCPT ); Fri, 21 Jun 2019 10:00:51 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x5LE0Vdf015471 for ; Fri, 21 Jun 2019 10:00:50 -0400 Received: from e06smtp02.uk.ibm.com (e06smtp02.uk.ibm.com [195.75.94.98]) by mx0a-001b2d01.pphosted.com with ESMTP id 2t8xamphuk-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Fri, 21 Jun 2019 10:00:46 -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 Date: Fri, 21 Jun 2019 16:00:32 +0200 From: Halil Pasic 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> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8bit Message-Id: <20190621160032.1bd0c15f.pasic@linux.ibm.com> Sender: linux-s390-owner@vger.kernel.org List-ID: To: Farhan Ali Cc: cohuck@redhat.com, farman@linux.ibm.com, linux-s390@vger.kernel.org, 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);