RDMA/mad: Fix possible memory leak in ib_mad_post_receive_mads()

If ib_dma_mapping_error() returns non-zero value,
ib_mad_post_receive_mads() will jump out of loops and return -ENOMEM
without freeing mad_priv. Fix this memory-leak problem by freeing mad_priv
in this case.

Fixes: 2c34e68f ("IB/mad: Check and handle potential DMA mapping errors")
Link: https://lore.kernel.org/r/20200612063824.180611-1-guofan5@huawei.comSigned-off-by: Fan Guo <guofan5@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/infiniband/core/mad.c

@@ -2718,6 +2718,7 @@ static int ib_mad_post_receive_mads(struct ib_mad_qp_info *qp_info,
 						 DMA_FROM_DEVICE);
 		if (unlikely(ib_dma_mapping_error(qp_info->port_priv->device,
 						  sg_list.addr))) {
+			kfree(mad_priv);
 			ret = -ENOMEM;
 			break;
 		}