[PATCH 4.19 03/79] RDMA/restrack: Release task struct which was hold by CM_ID object

[Greg Kroah-Hartman]

From: Leon Romanovsky <leo...@mellanox.com>

commit ed7a01fd3fd77f40b4ef2562b966a5decd8928d2 upstream.

Tracking CM_ID resource is performed in two stages: creation of cm_id
and connecting it to the cma_dev. It is needed because rdma-cm protocol
exports two separate user-visible calls rdma_create_id and rdma_accept.

At the time of CM_ID creation, the real owner of that object is unknown
yet and we need to grab task_struct. This task_struct is released or
reassigned in attach phase later on. but call to rdma_destroy_id left
this task_struct unreleased.

Such separation is unique to CM_ID and other restrack objects initialize
in one shot. It means that it is safe to use "res->valid" check to catch
unfinished CM_ID flow and release task_struct for that object.

Fixes: 00313983cda6 ("RDMA/nldev: provide detailed CM_ID information")
Reported-by: Artemy Kovalyov <artem...@mellanox.com>
Reviewed-by: Artemy Kovalyov <artem...@mellanox.com>
Reviewed-by: Yossi Itigin <yos...@mellanox.com>
Signed-off-by: Leon Romanovsky <leo...@mellanox.com>
Reviewed-by: Steve Wise <sw...@opengridcomputing.com>
Signed-off-by: Jason Gunthorpe <j...@mellanox.com>
Cc: Håkon Bugge <haakon.bu...@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 drivers/infiniband/core/cma.c      |    7 +++----
 drivers/infiniband/core/restrack.c |    6 ++++--
 2 files changed, 7 insertions(+), 6 deletions(-)

--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -1723,8 +1723,8 @@ void rdma_destroy_id(struct rdma_cm_id *
        mutex_lock(&id_priv->handler_mutex);
        mutex_unlock(&id_priv->handler_mutex);
 
+       rdma_restrack_del(&id_priv->res);
        if (id_priv->cma_dev) {
-               rdma_restrack_del(&id_priv->res);
                if (rdma_cap_ib_cm(id_priv->id.device, 1)) {
                        if (id_priv->cm_id.ib)
                                ib_destroy_cm_id(id_priv->cm_id.ib);
@@ -3463,10 +3463,9 @@ int rdma_bind_addr(struct rdma_cm_id *id
 
        return 0;
 err2:
-       if (id_priv->cma_dev) {
-               rdma_restrack_del(&id_priv->res);
+       rdma_restrack_del(&id_priv->res);
+       if (id_priv->cma_dev)
                cma_release_dev(id_priv);
-       }
 err1:
        cma_comp_exch(id_priv, RDMA_CM_ADDR_BOUND, RDMA_CM_IDLE);
        return ret;
--- a/drivers/infiniband/core/restrack.c
+++ b/drivers/infiniband/core/restrack.c
@@ -209,7 +209,7 @@ void rdma_restrack_del(struct rdma_restr
        struct ib_device *dev;
 
        if (!res->valid)
-               return;
+               goto out;
 
        dev = res_to_dev(res);
        if (!dev)
@@ -222,8 +222,10 @@ void rdma_restrack_del(struct rdma_restr
        down_write(&dev->res.rwsem);
        hash_del(&res->node);
        res->valid = false;
+       up_write(&dev->res.rwsem);
+
+out:
        if (res->task)
                put_task_struct(res->task);
-       up_write(&dev->res.rwsem);
 }
 EXPORT_SYMBOL(rdma_restrack_del);