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vfio: get rid of vfio_device_put()/vfio_group_get_device* races

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we really need to make sure that dropping the last reference happens
under the group->device_lock; otherwise a loop (under device_lock)
might find vfio_device instance that is being freed right now, has
already dropped the last reference and waits on device_lock to exclude
the sucker from the list.

Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2012-08-17 21:29:06 -04:00
parent 6d2cd3ce81
commit 90b1253e41
1 changed files with 1 additions and 2 deletions
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3
drivers/vfio/vfio.c
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@ -396,7 +396,6 @@ static void vfio_device_release(struct kref *kref)
struct vfio_device, kref);
struct vfio_group *group = device->group;
mutex_lock(&group->device_lock);
list_del(&device->group_next);
mutex_unlock(&group->device_lock);
@ -412,7 +411,7 @@ static void vfio_device_release(struct kref *kref)
static void vfio_device_put(struct vfio_device *device)
{
struct vfio_group *group = device->group;
kref_put(&device->kref, vfio_device_release);
kref_put_mutex(&device->kref, vfio_device_release, &group->device_lock);
vfio_group_put(group);
}