Re: [PATCH rdma-next v2 8/9] IB/cm: Add lock protection when access av/alt_av's port of a cm_id

[Jason Gunthorpe <jgg@nvidia.com>]

On Wed, Apr 21, 2021 at 02:40:38PM +0300, Leon Romanovsky wrote:
> @@ -303,20 +304,37 @@ static struct ib_mad_send_buf *cm_alloc_msg(struct cm_id_private *cm_id_priv)
>  	struct ib_mad_agent *mad_agent;
>  	struct ib_mad_send_buf *m;
>  	struct ib_ah *ah;
> +	int ret;
> +
> +	read_lock(&cm_id_priv->av_rwlock);
> +	if (!cm_id_priv->av.port) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
>  
>  	mad_agent = cm_id_priv->av.port->mad_agent;
> +	if (!mad_agent) {
> +		ret = -EINVAL;
> +		goto out;
> +	}
> +
>  	ah = rdma_create_ah(mad_agent->qp->pd, &cm_id_priv->av.ah_attr, 0);
> -	if (IS_ERR(ah))
> -		return (void *)ah;
> +	if (IS_ERR(ah)) {
> +		ret = PTR_ERR(ah);
> +		goto out;
> +	}
>  
>  	m = ib_create_send_mad(mad_agent, cm_id_priv->id.remote_cm_qpn,
>  			       cm_id_priv->av.pkey_index,
>  			       0, IB_MGMT_MAD_HDR, IB_MGMT_MAD_DATA,
>  			       GFP_ATOMIC,
>  			       IB_MGMT_BASE_VERSION);
> +
> +	read_unlock(&cm_id_priv->av_rwlock);
>  	if (IS_ERR(m)) {
>  		rdma_destroy_ah(ah, 0);
> -		return m;
> +		ret = PTR_ERR(m);
> +		goto out;
>  	}
>  
>  	/* Timeout set by caller if response is expected. */
> @@ -326,6 +344,10 @@ static struct ib_mad_send_buf *cm_alloc_msg(struct cm_id_private *cm_id_priv)
>  	refcount_inc(&cm_id_priv->refcount);
>  	m->context[0] = cm_id_priv;
>  	return m;
> +
> +out:
> +	read_unlock(&cm_id_priv->av_rwlock);

This flow has read_unlock happening twice on error

Jason