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authorAlex Williamson <alex.williamson@redhat.com>2013-06-25 16:06:54 -0600
committerAlex Williamson <alex.williamson@redhat.com>2013-06-25 16:06:54 -0600
commit6d6768c61b39a2184bc11bb0342e4f7f35642bcc (patch)
tree504f88a65c5ad214086ae2e3edff7bd4efcb548f /drivers
parentf5bfdbf252ad54aa4b6f765cbe89750087fcc155 (diff)
vfio: Limit group opens
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 <alex.williamson@redhat.com>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/vfio/vfio.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index 6d78736563d..d30f44da876 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;