[PATCH rdma-next 1/7] RDMA/cma: Fix unbalanced cm_id reference count during address resolve

[Leon Romanovsky <leon@kernel.org>]

From: Parav Pandit <parav@mellanox.com>

Below cited commit missed to consider AF_IB and loopback code flow in
rdma_resolve_addr().
This leads to unbalanced cm_id refcount in cma_work_handler() which
puts the refcount which was not incremented in rdma_resolve_addr().

A call trace is observed with such code flow.

BUG: unable to handle kernel NULL pointer dereference at (null)
[<ffffffff96b67e16>] __mutex_lock_slowpath+0x166/0x1d0
[<ffffffff96b6715f>] mutex_lock+0x1f/0x2f
[<ffffffffc0beabb5>] cma_work_handler+0x25/0xa0
[<ffffffff964b9ebf>] process_one_work+0x17f/0x440
[<ffffffff964baf56>] worker_thread+0x126/0x3c0

Hence, hold the cm_id reference when scheduling resolve work item.

Fixes: 722c7b2bfead ("RDMA/{cma, core}: Avoid callback on rdma_addr_cancel()")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
---
 drivers/infiniband/core/cma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/infiniband/core/cma.c b/drivers/infiniband/core/cma.c
index 55a9afacfedd..72f032160c4b 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -3148,6 +3148,7 @@ static int cma_resolve_loopback(struct rdma_id_private *id_priv)
 	rdma_addr_get_sgid(&id_priv->id.route.addr.dev_addr, &gid);
 	rdma_addr_set_dgid(&id_priv->id.route.addr.dev_addr, &gid);
 
+	atomic_inc(&id_priv->refcount);
 	cma_init_resolve_addr_work(work, id_priv);
 	queue_work(cma_wq, &work->work);
 	return 0;
@@ -3174,6 +3175,7 @@ static int cma_resolve_ib_addr(struct rdma_id_private *id_priv)
 	rdma_addr_set_dgid(&id_priv->id.route.addr.dev_addr, (union ib_gid *)
 		&(((struct sockaddr_ib *) &id_priv->id.route.addr.dst_addr)->sib_addr));
 
+	atomic_inc(&id_priv->refcount);
 	cma_init_resolve_addr_work(work, id_priv);
 	queue_work(cma_wq, &work->work);
 	return 0;
-- 
2.24.1