We do not protect the vfio_device::open_count with group_rwsem elsewhere (see vfio_device_fops_release as a comparison, where we already drop group_rwsem before open_count--). So move the group_rwsem unlock prior to open_count--. This change now also drops group_rswem before setting device->kvm = NULL, but that's also OK (again, just like vfio_device_fops_release). The setting of device->kvm before open_device is technically done while holding the group_rwsem, this is done to protect the group kvm value we are copying from, and we should not be relying on that to protect the contents of device->kvm; instead we assume this value will not change until after the device is closed and while under the dev_set->lock. Cc: Matthew Rosato <mjrosato@xxxxxxxxxxxxx> Cc: Jason Gunthorpe <jgg@xxxxxxxxxx> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx> Reviewed-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx> --- drivers/vfio/vfio.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- v2: - Remove Fixes tag (Kevin) - Add detailed description in commit message (Matthew, Jason) - Fix patch format (Jason) - Add r-b from Matthew v1: https://lore.kernel.org/kvm/20220620085459.200015-2-yi.l.liu@xxxxxxxxx/ --- diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c index 61e71c1154be..44c3bf8023ac 100644 --- a/drivers/vfio/vfio.c +++ b/drivers/vfio/vfio.c @@ -1146,10 +1146,10 @@ static struct file *vfio_device_open(struct vfio_device *device) if (device->open_count == 1 && device->ops->close_device) device->ops->close_device(device); err_undo_count: + up_read(&device->group->group_rwsem); device->open_count--; if (device->open_count == 0 && device->kvm) device->kvm = NULL; - up_read(&device->group->group_rwsem); mutex_unlock(&device->dev_set->lock); module_put(device->dev->driver->owner); err_unassign_container: -- 2.27.0
