[PATCH] net/rds: hold IB device reference through deferred cleanup

[Eduard Zateev <hackerowskiy@gmail.com>]

RDS device teardown queues rds_ib_dev_free() on rds_wq. Hold a
reference to the underlying IB device until deferred cleanup releases
its resources. This prevents device removal from freeing it while the
work is running.

Reported-by: syzbot+221e213bf17f17e0d6cd@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=221e213bf17f17e0d6cd
Signed-off-by: Eduard Zateev <hackerowskiy@gmail.com>
---
 net/rds/ib.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/rds/ib.c b/net/rds/ib.c
index 786f39169bc..597872e4fe9 100644
--- a/net/rds/ib.c
+++ b/net/rds/ib.c
@@ -115,6 +115,7 @@ static void rds_ib_dev_free(struct work_struct *work)
 
 	kfree(rds_ibdev->vector_load);
 
+	ib_device_put(rds_ibdev->dev);
 	kfree(rds_ibdev);
 }
 
@@ -142,6 +143,12 @@ static int rds_ib_add_one(struct ib_device *device)
 				 ibdev_to_node(device));
 	if (!rds_ibdev)
 		return -ENOMEM;
+	/* Keep the device registered until the deferred cleanup completes. */
+	if (!ib_device_try_get(device)) {
+		kfree(rds_ibdev);
+		return -ENODEV;
+	}
+	rds_ibdev->dev = device;
 
 	spin_lock_init(&rds_ibdev->spinlock);
 	refcount_set(&rds_ibdev->refcount, 1);
@@ -180,7 +187,6 @@ static int rds_ib_add_one(struct ib_device *device)
 		goto put_dev;
 	}
 
-	rds_ibdev->dev = device;
 	rds_ibdev->pd = ib_alloc_pd(device, 0);
 	if (IS_ERR(rds_ibdev->pd)) {
 		ret = PTR_ERR(rds_ibdev->pd);
-- 
2.55.0