From: Eli Cohen <elic@xxxxxxxxxx> 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@xxxxxxxxxx> Link: https://lore.kernel.org/r/20220321141303.9586-1-elic@xxxxxxxxxx Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- 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; } Patches currently in stable-queue which might be from elic@xxxxxxxxxx are queue-5.17/vdpa-mlx5-avoid-processing-works-if-workqueue-was-destroyed.patch