From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by ozlabs.org (Postfix) with ESMTP id 0FED92C0096 for ; Fri, 23 Aug 2013 13:33:37 +1000 (EST) Message-ID: <1377228807.25163.33.camel@ul30vt.home> Subject: Re: [PATCH] iommu: WARN_ON when removing a device with no iommu_group associated From: Alex Williamson To: Wei Yang Date: Thu, 22 Aug 2013 21:33:27 -0600 In-Reply-To: <1377222911-12144-1-git-send-email-weiyang@linux.vnet.ibm.com> References: <1377222911-12144-1-git-send-email-weiyang@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Cc: benh@au1.ibm.com, aik@ozlabs.ru, linux-kernel@vger.kernel.org, iommu , paulus@au1.ibm.com, linuxppc-dev@lists.ozlabs.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , [+cc iommu] On Fri, 2013-08-23 at 09:55 +0800, Wei Yang wrote: > When removing a device from the system, iommu_group driver will try to > disconnect it from its group. While in some cases, one device may not > associated with any iommu_group. For example, not enough DMA address space. > > In the generic bus notification, it will check dev->iommu_group before calling > iommu_group_remove_device(). While in some cases, developers may call > iommu_group_remove_device() in a different code path and without check. For > those devices with dev->iommu_group set to NULL, kernel will crash. > > This patch gives a warning and return when trying to remove a device from an > iommu_group with dev->iommu_group set to NULL. This helps to indicate some bad > behavior and also guard the kernel. > > Signed-off-by: Wei Yang Acked-by: Alex Williamson > --- > drivers/iommu/iommu.c | 3 +++ > 1 files changed, 3 insertions(+), 0 deletions(-) > > diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c > index fbe9ca7..43396f0 100644 > --- a/drivers/iommu/iommu.c > +++ b/drivers/iommu/iommu.c > @@ -379,6 +379,9 @@ void iommu_group_remove_device(struct device *dev) > struct iommu_group *group = dev->iommu_group; > struct iommu_device *tmp_device, *device = NULL; > > + if (WARN_ON(!group)) > + return; > + > /* Pre-notify listeners that a device is being removed. */ > blocking_notifier_call_chain(&group->notifier, > IOMMU_GROUP_NOTIFY_DEL_DEVICE, dev);