From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 Date: Tue, 9 Jul 2019 12:16:13 +0200 From: Cornelia Huck 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> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Farhan Ali Cc: farman@linux.ibm.com, pasic@linux.ibm.com, linux-s390@vger.kernel.org, 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