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    Subject[PATCH 5.17 1116/1126] vdpa/mlx5: Avoid processing works if workqueue was destroyed
    Date
    From: Eli Cohen <elic@nvidia.com>

    commit ad6dc1daaf29f97f23cc810d60ee01c0e83f4c6b upstream.

    If mlx5_vdpa gets unloaded while a VM is running, the workqueue will be
    destroyed. However, vhost might still have reference to the kick
    function and might attempt to push new works. This could lead to null
    pointer dereference.

    To fix this, set mvdev->wq to NULL just before destroying and verify
    that the workqueue is not NULL in mlx5_vdpa_kick_vq before attempting to
    push a new work.

    Fixes: 5262912ef3cf ("vdpa/mlx5: Add support for control VQ and MAC setting")
    Signed-off-by: Eli Cohen <elic@nvidia.com>
    Link: https://lore.kernel.org/r/20220321141303.9586-1-elic@nvidia.com
    Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/vdpa/mlx5/net/mlx5_vnet.c | 7 +++++--
    1 file changed, 5 insertions(+), 2 deletions(-)

    --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
    +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
    @@ -1669,7 +1669,7 @@ static void mlx5_vdpa_kick_vq(struct vdp
    return;

    if (unlikely(is_ctrl_vq_idx(mvdev, idx))) {
    - if (!mvdev->cvq.ready)
    + if (!mvdev->wq || !mvdev->cvq.ready)
    return;

    wqent = kzalloc(sizeof(*wqent), GFP_ATOMIC);
    @@ -2707,9 +2707,12 @@ static void mlx5_vdpa_dev_del(struct vdp
    struct mlx5_vdpa_mgmtdev *mgtdev = container_of(v_mdev, struct mlx5_vdpa_mgmtdev, mgtdev);
    struct mlx5_vdpa_dev *mvdev = to_mvdev(dev);
    struct mlx5_vdpa_net *ndev = to_mlx5_vdpa_ndev(mvdev);
    + struct workqueue_struct *wq;

    mlx5_notifier_unregister(mvdev->mdev, &ndev->nb);
    - destroy_workqueue(mvdev->wq);
    + wq = mvdev->wq;
    + mvdev->wq = NULL;
    + destroy_workqueue(wq);
    _vdpa_unregister_device(dev);
    mgtdev->ndev = NULL;
    }

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