Commit message: IB/core: Don't resolve passive side RoCE L2 address in CMA REQ handler

The code that resolves the passive side source MAC within the rdma_cm
connection request handler was both redundant and buggy, so remove it.

It was redundant since later, when an RC QP is modified to RTR state,
the resolution will take place in the ib_core module.  It was buggy
because this callback also deals with UD SIDR exchange, for which we
incorrectly looked at the REQ member of the CM event and dereferenced
a random value.

Fixes: dd5f03beb4f7 ("IB/core: Ethernet L2 attributes in verbs/cm structures")
Signed-off-by: Moni Shoua <monis@mellanox.com>
Signed-off-by: Or Gerlitz <ogerlitz@mellanox.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>
CVE: CVE-2014-2739
CWE: CWE-20
Vulnerability description: The cma_req_handler function in drivers/infiniband/core/cma.c in the Linux kernel 3.14.x through 3.14.1 attempts to resolve an RDMA over Converged Ethernet (aka RoCE) address that is properly resolved within a different module, which allows remote attackers to cause a denial of service (incorrect pointer dereference and system crash) via crafted network traffic.

Project: linux
File: cma.c

static int cma_req_handler(struct ib_cm_id *cm_id, struct ib_cm_event *ib_event)
{
 	struct rdma_id_private *listen_id, *conn_id;
 	struct rdma_cm_event event;
 	int offset, ret;
	u8 smac[ETH_ALEN];
	u8 alt_smac[ETH_ALEN];
	u8 *psmac = smac;
	u8 *palt_smac = alt_smac;
	int is_iboe = ((rdma_node_get_transport(cm_id->device->node_type) ==
			RDMA_TRANSPORT_IB) &&
		       (rdma_port_get_link_layer(cm_id->device,
			ib_event->param.req_rcvd.port) ==
			IB_LINK_LAYER_ETHERNET));
 
 	listen_id = cm_id->context;
 	if (!cma_check_req_qp_type(&listen_id->id, ib_event))
		return -EINVAL;

	if (cma_disable_callback(listen_id, RDMA_CM_LISTEN))
		return -ECONNABORTED;

	memset(&event, 0, sizeof event);
	offset = cma_user_data_offset(listen_id);
	event.event = RDMA_CM_EVENT_CONNECT_REQUEST;
	if (ib_event->event == IB_CM_SIDR_REQ_RECEIVED) {
		conn_id = cma_new_udp_id(&listen_id->id, ib_event);
		event.param.ud.private_data = ib_event->private_data + offset;
		event.param.ud.private_data_len =
				IB_CM_SIDR_REQ_PRIVATE_DATA_SIZE - offset;
	} else {
		conn_id = cma_new_conn_id(&listen_id->id, ib_event);
		cma_set_req_event_data(&event, &ib_event->param.req_rcvd,
				       ib_event->private_data, offset);
	}
	if (!conn_id) {
		ret = -ENOMEM;
		goto err1;
	}

	mutex_lock_nested(&conn_id->handler_mutex, SINGLE_DEPTH_NESTING);
	ret = cma_acquire_dev(conn_id, listen_id);
	if (ret)
		goto err2;

	conn_id->cm_id.ib = cm_id;
	cm_id->context = conn_id;
	cm_id->cm_handler = cma_ib_handler;

	/*
	 * Protect against the user destroying conn_id from another thread
	 * until we're done accessing it.
	 */
	atomic_inc(&conn_id->refcount);
 	ret = conn_id->id.event_handler(&conn_id->id, &event);
 	if (ret)
 		goto err3;
	if (is_iboe) {
		if (ib_event->param.req_rcvd.primary_path != NULL)
			rdma_addr_find_smac_by_sgid(
				&ib_event->param.req_rcvd.primary_path->sgid,
				psmac, NULL);
		else
			psmac = NULL;
		if (ib_event->param.req_rcvd.alternate_path != NULL)
			rdma_addr_find_smac_by_sgid(
				&ib_event->param.req_rcvd.alternate_path->sgid,
				palt_smac, NULL);
		else
			palt_smac = NULL;
	}
 	/*
 	 * Acquire mutex to prevent user executing rdma_destroy_id()
 	 * while we're accessing the cm_id.
 	 */
 	mutex_lock(&lock);
	if (is_iboe)
		ib_update_cm_av(cm_id, psmac, palt_smac);
 	if (cma_comp(conn_id, RDMA_CM_CONNECT) &&
 	    (conn_id->id.qp_type != IB_QPT_UD))
 		ib_send_cm_mra(cm_id, CMA_CM_MRA_SETTING, NULL, 0);
	mutex_unlock(&lock);
	mutex_unlock(&conn_id->handler_mutex);
	mutex_unlock(&listen_id->handler_mutex);
	cma_deref_id(conn_id);
	return 0;

err3:
	cma_deref_id(conn_id);
	/* Destroy the CM ID by returning a non-zero value. */
	conn_id->cm_id.ib = NULL;
err2:
	cma_exch(conn_id, RDMA_CM_DESTROYING);
	mutex_unlock(&conn_id->handler_mutex);
err1:
	mutex_unlock(&listen_id->handler_mutex);
	if (conn_id)
		rdma_destroy_id(&conn_id->id);
	return ret;
}