[PATCH net-next 5/7] ibmveth: release the pool kobjects when probe fails

[Mingming Cao <mmc@linux.ibm.com>]

If register_netdev() fails in ibmveth_probe(), for example with -EINTR
when the binding task is killed, probe frees the netdev but leaves the
pool%d kobjects embedded in it registered in sysfs. Reading
/sys/devices/vio/<unit>/pool0/num is then a use-after-free, and the
next probe cannot add pool0.

Put the kobjects before freeing the netdev, as ibmveth_remove() does,
on this path and on the netif_set_real_num_tx_queues() one.

As in remove(), the kobjects have no release(), so with
CONFIG_DEBUG_KOBJECT_RELEASE their deferred cleanup, including
removing the sysfs files, can still run after the free.

Tested on a POWER10 LPAR with register_netdev() forced to fail with
-EINTR: no pool%d directories remain and the device binds again.

Fixes: 860f242eb534 ("[PATCH] ibmveth change buffer pools dynamically")
Signed-off-by: Mingming Cao <mmc@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmveth.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/ibm/ibmveth.c b/drivers/net/ethernet/ibm/ibmveth.c
index b89ce389d951..d5ba2f2650d0 100644
--- a/drivers/net/ethernet/ibm/ibmveth.c
+++ b/drivers/net/ethernet/ibm/ibmveth.c
@@ -1965,8 +1965,7 @@ static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
 	if (rc) {
 		netdev_dbg(netdev, "failed to set number of tx queues rc=%d\n",
 			   rc);
-		free_netdev(netdev);
-		return rc;
+		goto err_put_pools;
 	}
 	adapter->tx_ltb_size = PAGE_ALIGN(IBMVETH_MAX_TX_BUF_SIZE);
 	for (i = 0; i < IBMVETH_MAX_QUEUES; i++)
@@ -1981,13 +1980,18 @@ static int ibmveth_probe(struct vio_dev *dev, const struct vio_device_id *id)
 
 	if (rc) {
 		netdev_dbg(netdev, "failed to register netdev rc=%d\n", rc);
-		free_netdev(netdev);
-		return rc;
+		goto err_put_pools;
 	}
 
 	netdev_dbg(netdev, "registered\n");
 
 	return 0;
+
+err_put_pools:
+	for (i = 0; i < IBMVETH_NUM_BUFF_POOLS; i++)
+		kobject_put(&adapter->rx_buff_pool[i].kobj);
+	free_netdev(netdev);
+	return rc;
 }
 
 static void ibmveth_remove(struct vio_dev *dev)
-- 
2.39.3 (Apple Git-146)