crypto/ipsec_mb: fix queue setup null pointer dereference

When setting up a qp in a secondary process, the local qp pointer is set
to the stored device qp, configured by the primary process for that
device, but only if that device qp is not NULL.
If the device qp was not set up correctly by the primary process and has
a NULL value, the local qp variable stays at the default initialised
value, NULL. This causes a NULL pointer dereference later in the
function when using the qp value.

This is fixed by always setting the local qp to the value of the device
qp stored, and then checking if qp is NULL, returning an error if it is.

Coverity issue: 374382
Fixes: 72a1692 ("crypto/ipsec_mb: support multi-process")
Cc: stable@dpdk.org

Signed-off-by: Ciara Power <ciara.power@intel.com>
Acked-by: Fan Zhang <roy.fan.zhang@intel.com>

drivers/crypto/ipsec_mb/ipsec_mb_ops.c

@@ -221,8 +221,11 @@ ipsec_mb_qp_setup(struct rte_cryptodev *dev, uint16_t qp_id,
 				IMB_VERSION_STR, IMB_MP_REQ_VER_STR);
 		return -EINVAL;
 #endif
-		if (dev->data->queue_pairs[qp_id] != NULL)
-			qp = dev->data->queue_pairs[qp_id];
+		qp = dev->data->queue_pairs[qp_id];
+		if (qp == NULL) {
+			IPSEC_MB_LOG(ERR, "Primary process hasn't configured device qp.");
+			return -EINVAL;
+		}
 	} else {
 		/* Free memory prior to re-allocation if needed. */
 		if (dev->data->queue_pairs[qp_id] != NULL)