RDMA/nes: Fix for crash when registering zero length MR for CQ

Signed-off-by: Tatyana Nikolova <Tatyana.E.Nikolova@intel.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>

drivers/infiniband/hw/nes/nes_verbs.c

@@ -2561,6 +2561,11 @@ static struct ib_mr *nes_reg_user_mr(struct ib_pd *pd, u64 start, u64 length,
 			return ibmr;
 		case IWNES_MEMREG_TYPE_QP:
 		case IWNES_MEMREG_TYPE_CQ:
+			if (!region->length) {
+				nes_debug(NES_DBG_MR, "Unable to register zero length region for CQ\n");
+				ib_umem_release(region);
+				return ERR_PTR(-EINVAL);
+			}
 			nespbl = kzalloc(sizeof(*nespbl), GFP_KERNEL);
 			if (!nespbl) {
 				nes_debug(NES_DBG_MR, "Unable to allocate PBL\n");