From 77808fe7d03ad0062840b95f431869a8b3d88b24 Mon Sep 17 00:00:00 2001 From: Sven Eckelmann Date: Mon, 16 Feb 2026 11:20:29 +0100 Subject: batman-adv: Avoid double-rtnl_lock ELP metric worker MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit commit cfc83a3c71517b59c1047db57da31e26a9dc2f33 upstream. batadv_v_elp_get_throughput() might be called when the RTNL lock is already held. This could be problematic when the work queue item is cancelled via cancel_delayed_work_sync() in batadv_v_elp_iface_disable(). In this case, an rtnl_lock() would cause a deadlock. To avoid this, rtnl_trylock() was used in this function to skip the retrieval of the ethtool information in case the RTNL lock was already held. But for cfg80211 interfaces, batadv_get_real_netdev() was called - which also uses rtnl_lock(). The approach for __ethtool_get_link_ksettings() must also be used instead and the lockless version __batadv_get_real_netdev() has to be called. Cc: stable@vger.kernel.org Fixes: 8c8ecc98f5c6 ("batman-adv: Drop unmanaged ELP metric worker") Reported-by: Christian Schmidbauer Signed-off-by: Sven Eckelmann Tested-by: Sören Skaarup Signed-off-by: Simon Wunderlich Signed-off-by: Greg Kroah-Hartman --- net/batman-adv/bat_v_elp.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'net/batman-adv/bat_v_elp.c') diff --git a/net/batman-adv/bat_v_elp.c b/net/batman-adv/bat_v_elp.c index cb16c1ed2a58..fe832093d421 100644 --- a/net/batman-adv/bat_v_elp.c +++ b/net/batman-adv/bat_v_elp.c @@ -111,7 +111,15 @@ static bool batadv_v_elp_get_throughput(struct batadv_hardif_neigh_node *neigh, /* unsupported WiFi driver version */ goto default_throughput; - real_netdev = batadv_get_real_netdev(hard_iface->net_dev); + /* only use rtnl_trylock because the elp worker will be cancelled while + * the rntl_lock is held. the cancel_delayed_work_sync() would otherwise + * wait forever when the elp work_item was started and it is then also + * trying to rtnl_lock + */ + if (!rtnl_trylock()) + return false; + real_netdev = __batadv_get_real_netdev(hard_iface->net_dev); + rtnl_unlock(); if (!real_netdev) goto default_throughput; -- cgit v1.2.3