Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1946084Ab3FUVMu (ORCPT ); Fri, 21 Jun 2013 17:12:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:50948 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945954Ab3FUVMs (ORCPT ); Fri, 21 Jun 2013 17:12:48 -0400 Subject: [PATCH] vfio: Limit group opens To: alex.williamson@redhat.com From: Alex Williamson Cc: aik@ozlabs.ru, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Date: Fri, 21 Jun 2013 15:12:44 -0600 Message-ID: <20130621211144.8237.7370.stgit@bling.home> User-Agent: StGit/0.16 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2443 Lines: 73 vfio_group_fops_open attempts to limit concurrent sessions by disallowing opens once group->container is set. This really doesn't do what we want and allow for inconsistent behavior, for instance a group can be opened twice, then a container set giving the user two file descriptors to the group. But then it won't allow more to be opened. There's not much reason to have the group opened multiple times since most access is through devices or the container, so complete what the original code intended and only allow a single instance. Signed-off-by: Alex Williamson --- drivers/vfio/vfio.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 6d78736..d30f44d 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -76,6 +76,7 @@ struct vfio_group { struct notifier_block nb; struct list_head vfio_next; struct list_head container_next; + atomic_t opened; }; struct vfio_device { @@ -206,6 +207,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group) INIT_LIST_HEAD(&group->device_list); mutex_init(&group->device_lock); atomic_set(&group->container_users, 0); + atomic_set(&group->opened, 0); group->iommu_group = iommu_group; group->nb.notifier_call = vfio_iommu_group_notifier; @@ -1236,12 +1238,22 @@ static long vfio_group_fops_compat_ioctl(struct file *filep, static int vfio_group_fops_open(struct inode *inode, struct file *filep) { struct vfio_group *group; + int opened; group = vfio_group_get_from_minor(iminor(inode)); if (!group) return -ENODEV; + /* Do we need multiple instances of the group open? Seems not. */ + opened = atomic_cmpxchg(&group->opened, 0, 1); + if (opened) { + vfio_group_put(group); + return -EBUSY; + } + + /* Is something still in use from a previous open? */ if (group->container) { + atomic_dec(&group->opened); vfio_group_put(group); return -EBUSY; } @@ -1259,6 +1271,8 @@ static int vfio_group_fops_release(struct inode *inode, struct file *filep) vfio_group_try_dissolve_container(group); + atomic_dec(&group->opened); + vfio_group_put(group); return 0; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/