mlxsw: core: Increase scope of RCU read-side critical section

BugLink: https://bugs.launchpad.net/bugs/1892822

[ Upstream commit 7d8e8f34 ]

The lifetime of the Rx listener item ('rxl_item') is managed using RCU,
but is dereferenced outside of RCU read-side critical section, which can
lead to a use-after-free.

Fix this by increasing the scope of the RCU read-side critical section.

Fixes: 93c1edb2 ("mlxsw: Introduce Mellanox switch driver core")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/net/ethernet/mellanox/mlxsw/core.c

@@ -1208,9 +1208,10 @@ void mlxsw_core_skb_receive(struct mlxsw_core *mlxsw_core, struct sk_buff *skb,
 			break;
 		}
 	}
+	if (!found) {
 		rcu_read_unlock();
-	if (!found)
 		goto drop;
+	}
 
 	pcpu_stats = this_cpu_ptr(mlxsw_core->pcpu_stats);
 	u64_stats_update_begin(&pcpu_stats->syncp);
@@ -1221,6 +1222,7 @@ void mlxsw_core_skb_receive(struct mlxsw_core *mlxsw_core, struct sk_buff *skb,
 	u64_stats_update_end(&pcpu_stats->syncp);
 
 	rxl->func(skb, local_port, rxl_item->priv);
+	rcu_read_unlock();
 	return;
 
 drop: