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Date:   Fri, 14 Feb 2020 10:41:51 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Parav Pandit <parav@...lanox.com>,
        Leon Romanovsky <leonro@...lanox.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Sasha Levin <sashal@...nel.org>, linux-rdma@...r.kernel.org
Subject: [PATCH AUTOSEL 5.5 119/542] RDMA/cma: Fix unbalanced cm_id reference count during address resolve

From: Parav Pandit <parav@...lanox.com>

[ Upstream commit b4fb4cc5ba83b20dae13cef116c33648e81d2f44 ]

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

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 the resolve work item.

Fixes: 722c7b2bfead ("RDMA/{cma, core}: Avoid callback on rdma_addr_cancel()")
Link: https://lore.kernel.org/r/20200126142652.104803-2-leon@kernel.org
Signed-off-by: Parav Pandit <parav@...lanox.com>
Signed-off-by: Leon Romanovsky <leonro@...lanox.com>
Reviewed-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Jason Gunthorpe <jgg@...lanox.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 43a6f07e0afe2..af1afc17b8bdf 100644
--- a/drivers/infiniband/core/cma.c
+++ b/drivers/infiniband/core/cma.c
@@ -3118,6 +3118,7 @@ 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;
@@ -3144,6 +3145,7 @@ 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;
-- 
2.20.1

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