On Mon, 21 Mar 2022 14:04:28 +0800 Jason Wang wrote:
> A userspace triggerable infinite loop could happen in
> mlx5_cvq_kick_handler() if userspace keeps sending a huge amount of
> cvq requests.
>
> Fixing this by introducing a quota and re-queue the work if we're out
> of the budget. While at it, using a per device workqueue to avoid on
> demand memory allocation for cvq.
>
> Fixes: 5262912ef3cfc ("vdpa/mlx5: Add support for control VQ and MAC setting")
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> drivers/vdpa/mlx5/net/mlx5_vnet.c | 28 +++++++++++++++-------------
> 1 file changed, 15 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> index d0f91078600e..d5a6fb3f9c41 100644
> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
> @@ -163,6 +163,7 @@ struct mlx5_vdpa_net {
> u32 cur_num_vqs;
> struct notifier_block nb;
> struct vdpa_callback config_cb;
> + struct mlx5_vdpa_wq_ent cvq_ent;
> };
>
> static void free_resources(struct mlx5_vdpa_net *ndev);
> @@ -1600,6 +1601,8 @@ static virtio_net_ctrl_ack handle_ctrl_mq(struct
> mlx5_vdpa_dev *mvdev, u8 cmd)
> return status;
> }
>
> +#define MLX5_CVQ_BUDGET 16
> +
This is not needed as given a single thread workqueue, a cond_resched()
can do the job in the worker context instead of requeue of work.
Hillf
> static void mlx5_cvq_kick_handler(struct work_struct *work)
> {
> virtio_net_ctrl_ack status = VIRTIO_NET_ERR;
> @@ -1609,17 +1612,17 @@ static void mlx5_cvq_kick_handler(struct work_struct
> *work)
> struct mlx5_control_vq *cvq;
> struct mlx5_vdpa_net *ndev;
> size_t read, write;
> - int err;
> + int err, n = 0;
>
> wqent = container_of(work, struct mlx5_vdpa_wq_ent, work);
> mvdev = wqent->mvdev;
> ndev = to_mlx5_vdpa_ndev(mvdev);
> cvq = &mvdev->cvq;
> if (!(ndev->mvdev.actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ)))
> - goto out;
> + return;
>
> if (!cvq->ready)
> - goto out;
> + return;
>
> while (true) {
> err = vringh_getdesc_iotlb(&cvq->vring, &cvq->riov, &cvq->wiov,
> &cvq->head,
> @@ -1653,9 +1656,13 @@ static void mlx5_cvq_kick_handler(struct work_struct
> *work)
>
> if (vringh_need_notify_iotlb(&cvq->vring))
> vringh_notify(&cvq->vring);
> +
> + n++;
> + if (n > MLX5_CVQ_BUDGET) {
> + queue_work(mvdev->wq, &wqent->work);
> + break;
> + }
> }
> -out:
> - kfree(wqent);
> }
>
> static void mlx5_vdpa_kick_vq(struct vdpa_device *vdev, u16 idx)
> @@ -1663,7 +1670,6 @@ static void mlx5_vdpa_kick_vq(struct vdpa_device *vdev,
> u16 idx)
> struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev);
> struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
> struct mlx5_vdpa_virtqueue *mvq;
> - struct mlx5_vdpa_wq_ent *wqent;
>
> if (!is_index_valid(mvdev, idx))
> return;
> @@ -1672,13 +1678,7 @@ static void mlx5_vdpa_kick_vq(struct vdpa_device
> *vdev, u16 idx)
> if (!mvdev->cvq.ready)
> return;
>
> - wqent = kzalloc(sizeof(*wqent), GFP_ATOMIC);
> - if (!wqent)
> - return;
> -
> - wqent->mvdev = mvdev;
> - INIT_WORK(&wqent->work, mlx5_cvq_kick_handler);
> - queue_work(mvdev->wq, &wqent->work);
> + queue_work(mvdev->wq, &ndev->cvq_ent.work);
> return;
> }
>
> @@ -2668,6 +2668,8 @@ static int mlx5_vdpa_dev_add(struct vdpa_mgmt_dev
> *v_mdev, const char *name,
> if (err)
> goto err_mr;
>
> + ndev->cvq_ent.mvdev = mvdev;
> + INIT_WORK(&ndev->cvq_ent.work, mlx5_cvq_kick_handler);
> mvdev->wq = create_singlethread_workqueue("mlx5_vdpa_wq");
> if (!mvdev->wq) {
> err = -ENOMEM;
> --
> 2.18.1
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