[PATCH net] net/mlx5: IPOIB, Fix QPN lookup race

[Prathamesh Deshpande <prathameshdeshpande7@gmail.com>]

mlx5i_pkey_get_netdev() reads the QPN hash table without ht_lock,
while mlx5i_pkey_del_qpn() removes entries under that lock and then
frees them.

PKEY child interfaces share the parent's RX resources, so RX lookups
can overlap child removal and access a freed entry. A lookup for
another QPN in the same bucket can also be affected.

Hold ht_lock during lookup and save node->netdev before unlocking.

Fixes: 7e7f4780c340 ("net/mlx5e: IPoIB, Use hash-table to map between QPN to child netdev")
Signed-off-by: Prathamesh Deshpande <prathameshdeshpande7@gmail.com>
---
 .../ethernet/mellanox/mlx5/core/ipoib/ipoib_vlan.c   | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib_vlan.c b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib_vlan.c
index 4120afd097c3..6c24ae8e7662 100644
--- a/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib_vlan.c
+++ b/drivers/net/ethernet/mellanox/mlx5/core/ipoib/ipoib_vlan.c
@@ -126,13 +126,17 @@ int mlx5i_pkey_del_qpn(struct net_device *netdev, u32 qpn)
 struct net_device *mlx5i_pkey_get_netdev(struct net_device *netdev, u32 qpn)
 {
 	struct mlx5i_priv *ipriv = netdev_priv(netdev);
+	struct mlx5i_pkey_qpn_ht *ht = ipriv->qpn_htbl;
+	struct net_device *result = NULL;
 	struct qpn_to_netdev *node;
 
-	node = mlx5i_find_qpn_to_netdev_node(ipriv->qpn_htbl->buckets, qpn);
-	if (!node)
-		return NULL;
+	spin_lock_bh(&ht->ht_lock);
+	node = mlx5i_find_qpn_to_netdev_node(ht->buckets, qpn);
+	if (node)
+		result = node->netdev;
+	spin_unlock_bh(&ht->ht_lock);
 
-	return node->netdev;
+	return result;
 }
 
 static int mlx5i_pkey_open(struct net_device *netdev);
-- 
2.43.0