Re: [PATCH v2 13/14] vfio: Add ioctls for device cdev using iommufd

Yan Zhao
2023-02-07T04:05:07Z

On Mon, Feb 06, 2023 at 01:05:31AM -0800, Yi Liu wrote:
...

> +void vfio_device_cdev_close(struct vfio_device_file *df)
> +{
> + mutex_lock(&df->device->dev_set->lock);
> + vfio_device_close(df);
> + vfio_device_put_kvm(df->device);
> + mutex_unlock(&df->device->dev_set->lock);
> +}
> +

...

> +long vfio_device_ioctl_bind_iommufd(struct vfio_device_file *df,
> + unsigned long arg)
> +{
> + struct vfio_device *device = df->device;
> + struct vfio_device_bind_iommufd bind;
> + struct iommufd_ctx *iommufd = NULL;
> + unsigned long minsz;
> + struct fd f;
> + int ret;
> +
> + minsz = offsetofend(struct vfio_device_bind_iommufd, iommufd);
> +
> + if (copy_from_user(&bind, (void __user *)arg, minsz))
> + return -EFAULT;
> +
> + if (bind.argsz < minsz || bind.flags)
> + return -EINVAL;
> +
> + if (!device->ops->bind_iommufd)
> + return -ENODEV;
> +
> + mutex_lock(&device->dev_set->lock);
> + /*
> + * If already been bound to an iommufd, or already set noiommu
> + * then fail it.
> + */
> + if (df->iommufd || df->noiommu) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + /* iommufd < 0 means noiommu mode */
> + if (bind.iommufd < 0) {
> + if (!capable(CAP_SYS_RAWIO)) {
> + ret = -EPERM;
> + goto out_unlock;
> + }
> + df->noiommu = true;
> + } else {
> + f = fdget(bind.iommufd);
> + if (!f.file) {
> + ret = -EBADF;
> + goto out_unlock;
> + }
> + iommufd = iommufd_ctx_from_file(f.file);
> + if (IS_ERR(iommufd)) {
> + ret = PTR_ERR(iommufd);
> + goto out_put_file;
> + }
> + }
> +
> + /*
> + * Before the first device open, get the KVM pointer currently
> + * associated with the device file (if there is) and obtain a
> + * reference. This reference is held until device closed. Save
> + * the pointer in the device for use by drivers.
> + */
> + vfio_device_get_kvm_safe(df);
> +
> + df->iommufd = iommufd;
> + ret = vfio_device_open(df, &bind.out_devid, NULL);
> + if (ret)
> + goto out_put_kvm;
> +
> + ret = copy_to_user((void __user *)arg + minsz,
> + &bind.out_devid,
> + sizeof(bind.out_devid)) ? -EFAULT : 0;
> + if (ret)
> + goto out_close_device;
> +
> + if (iommufd)
> + fdput(f);
> + else if (df->noiommu)
> + dev_warn(device->dev, "vfio-noiommu device used by user "
> + "(%s:%d)\n", current->comm, task_pid_nr(current));
> + mutex_unlock(&device->dev_set->lock);
> + return 0;
> +
> +out_close_device:
> + vfio_device_close(df);
vfio_device_close() is called here if any error after vfio_device_open().
But it will also be called unconditionally in vfio_device_cdev_close() and
cause a wrong value of device->open_count.

df->access_granted in patch 07 can also be of wrong true value after
this vfio_device_close().

> +out_put_kvm:
> + vfio_device_put_kvm(device);
> +out_put_file:
> + if (iommufd)
> + fdput(f);
> +out_unlock:
> + df->iommufd = NULL;
> + df->noiommu = false;
> + mutex_unlock(&device->dev_set->lock);
> + return ret;
> +}
> +