[PATCH rdma-rc v3] RDMA/core: Always release restrack object

[Leon Romanovsky <leon@kernel.org>]

From: Leon Romanovsky <leonro@nvidia.com>

Change location of rdma_restrack_del() to fix the bug where
task_struct was acquired but not released, causing to resource leak.

  ucma_create_id() {
    ucma_alloc_ctx();
    rdma_create_user_id() {
      rdma_restrack_new();
      rdma_restrack_set_name() {
        rdma_restrack_attach_task.part.0(); <--- task_struct was gotten
      }
    }
    ucma_destroy_private_ctx() {
      ucma_put_ctx();
      rdma_destroy_id() {
        _destroy_id()                       <--- id_priv was freed
      }
    }
  }

Fixes: 889d916b6f8a ("RDMA/core: Don't access cm_id after its destruction")
Reported-by: Pavel Skripkin <paskripkin@gmail.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
---
Changelog:
v3:
 * Dropped controversial hunks and updated commit message respectively
v2: https://lore.kernel.org/lkml/e2eed941f912b2068e371fd37f43b8cf5082a0e6.1623129597.git.leonro@nvidia.com
 * Added bug report analysis
v1: https://lore.kernel.org/linux-rdma/f72e27d5c82cd9beec7670141afa62786836c569.1622956637.git.leonro@nvidia.com/T/#u
---
 drivers/infiniband/core/cma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index ab148a696c0c..6d103c42bbec 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -1852,6 +1852,7 @@ static void _destroy_id(struct rdma_id_private *id_priv,
 {
 	cma_cancel_operation(id_priv, state);
 
+	rdma_restrack_del(&id_priv->res);
 	if (id_priv->cma_dev) {
 		if (rdma_cap_ib_cm(id_priv->id.device, 1)) {
 			if (id_priv->cm_id.ib)
@@ -1861,7 +1862,6 @@ static void _destroy_id(struct rdma_id_private *id_priv,
 				iw_destroy_cm_id(id_priv->cm_id.iw);
 		}
 		cma_leave_mc_groups(id_priv);
-		rdma_restrack_del(&id_priv->res);
 		cma_release_dev(id_priv);
 	}
 
-- 
2.31.1