RDMA/rtrs: Fix the last iu->buf leak in err path

The last iu->buf will leak if ib_dma_mapping_error() fails.

Fixes: c0894b3e ("RDMA/rtrs: core: lib functions shared between client and server modules")
Link: https://lore.kernel.org/r/1682384563-2-3-git-send-email-lizhijian@fujitsu.comSigned-off-by: Li Zhijian <lizhijian@fujitsu.com>
Acked-by: Guoqing Jiang <guoqing.jiang@linux.dev>
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/ulp/rtrs/rtrs.c

@@ -37,8 +37,10 @@ struct rtrs_iu *rtrs_iu_alloc(u32 iu_num, size_t size, gfp_t gfp_mask,
 			goto err;
 
 		iu->dma_addr = ib_dma_map_single(dma_dev, iu->buf, size, dir);
-		if (ib_dma_mapping_error(dma_dev, iu->dma_addr))
+		if (ib_dma_mapping_error(dma_dev, iu->dma_addr)) {
+			kfree(iu->buf);
 			goto err;
+		}
 
 		iu->cqe.done  = done;
 		iu->size      = size;