From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:26642 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725947AbfGINsj (ORCPT ); Tue, 9 Jul 2019 09:48:39 -0400 Subject: Re: [RFC v2 4/5] vfio-ccw: Don't call cp_free if we are processing a channel program References: <1405df8415d3bff446c22753d0e9b91ff246eb0f.1562616169.git.alifm@linux.ibm.com> <20190709121613.6a3554fa.cohuck@redhat.com> From: Farhan Ali Message-ID: <45ad7230-3674-2601-af5b-d9beef9312be@linux.ibm.com> Date: Tue, 9 Jul 2019 09:46:51 -0400 MIME-Version: 1.0 In-Reply-To: <20190709121613.6a3554fa.cohuck@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Cornelia Huck Cc: farman@linux.ibm.com, pasic@linux.ibm.com, linux-s390@vger.kernel.org, kvm@vger.kernel.org On 07/09/2019 06:16 AM, Cornelia Huck wrote: > 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? > I think the problem was always there. >> >> 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 > > Thanks for reviewing. Thanks Farhan