RDMA/ucma: Fix resource leak on error path

In ucma_process_join(), if the call to xa_alloc() fails, the function will
return without freeing mc. Fix this by jumping to the correct line.

In the process I renamed the jump labels to something more memorable for
extra clarity.

Link: https://lore.kernel.org/r/20200902162454.332828-1-alex.dewar90@gmail.com
Addresses-Coverity-ID: 1496814 ("Resource leak")
Fixes: 95fe5109 ("RDMA/ucma: Remove mc_list and rely on xarray")
Signed-off-by: Alex Dewar <alex.dewar90@gmail.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>

drivers/infiniband/core/ucma.c

@@ -1453,7 +1453,7 @@ static ssize_t ucma_process_join(struct ucma_file *file,
 	mc = kzalloc(sizeof(*mc), GFP_KERNEL);
 	if (!mc) {
 		ret = -ENOMEM;
-		goto err1;
+		goto err_put_ctx;
 	}
 
 	mc->ctx = ctx;
@@ -1464,7 +1464,7 @@ static ssize_t ucma_process_join(struct ucma_file *file,
 	if (xa_alloc(&multicast_table, &mc->id, NULL, xa_limit_32b,
 		     GFP_KERNEL)) {
 		ret = -ENOMEM;
-		goto err1;
+		goto err_free_mc;
 	}
 
 	mutex_lock(&ctx->mutex);
@@ -1472,13 +1472,13 @@ static ssize_t ucma_process_join(struct ucma_file *file,
 				  join_state, mc);
 	mutex_unlock(&ctx->mutex);
 	if (ret)
-		goto err2;
+		goto err_xa_erase;
 
 	resp.id = mc->id;
 	if (copy_to_user(u64_to_user_ptr(cmd->response),
 			 &resp, sizeof(resp))) {
 		ret = -EFAULT;
-		goto err3;
+		goto err_leave_multicast;
 	}
 
 	xa_store(&multicast_table, mc->id, mc, 0);
@@ -1486,15 +1486,16 @@ static ssize_t ucma_process_join(struct ucma_file *file,
 	ucma_put_ctx(ctx);
 	return 0;
 
-err3:
+err_leave_multicast:
 	mutex_lock(&ctx->mutex);
 	rdma_leave_multicast(ctx->cm_id, (struct sockaddr *) &mc->addr);
 	mutex_unlock(&ctx->mutex);
 	ucma_cleanup_mc_events(mc);
-err2:
+err_xa_erase:
 	xa_erase(&multicast_table, mc->id);
+err_free_mc:
 	kfree(mc);
-err1:
+err_put_ctx:
 	ucma_put_ctx(ctx);
 	return ret;
 }