From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.simonwunderlich.de (mail.simonwunderlich.de [23.88.38.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 091CE327BF5; Wed, 25 Feb 2026 08:56:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=23.88.38.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772009767; cv=none; b=kY+OUSvOA4RnK06DkhyFciZvAj1EYTuxIeDY+5Mz56YVRVc8kv6ot4PBR01BWag043cpbUfTamQMUQe3vW06HdMkztFjBZC5Otd4xVtJ/g2n+q7tsB8Bnmfga5ntPpyG6QI2VydiStXfa1DlJNNkbzSp25pOdQDOnhxKVk5LkmU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772009767; c=relaxed/simple; bh=dn+ym0kXKKxokqG3vOb3SAHDZY+C1UCD/bpVcpbn/VI=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=KYtULk2xmorBU1y98T/1hRHnWDQXUh9rrlNxiBsr78jgY7bd7DBeylMZoR2B0K7+v1da0WMRtTvJkhizoo/2gd5z1ibIwcar0OaGx8muQm5zROCB1RdePhHWfs2VjsZ+3iARXAZWN2lhCA4588Kt9sBPWZkAa8tL8MC3OzFpBN0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=simonwunderlich.de; spf=pass smtp.mailfrom=simonwunderlich.de; arc=none smtp.client-ip=23.88.38.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=simonwunderlich.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=simonwunderlich.de Received: from kero.packetmixer.de (p200300C5970D83d820Ce3bC4F6cb317e.dip0.t-ipconnect.de [IPv6:2003:c5:970d:83d8:20ce:3bc4:f6cb:317e]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.simonwunderlich.de (Postfix) with ESMTPSA id 0245FFA130; Wed, 25 Feb 2026 09:46:18 +0100 (CET) From: Simon Wunderlich To: davem@davemloft.net, kuba@kernel.org Cc: netdev@vger.kernel.org, b.a.t.m.a.n@lists.open-mesh.org, Sven Eckelmann , stable@vger.kernel.org, Christian Schmidbauer , =?UTF-8?q?S=C3=B6ren=20Skaarup?= , Simon Wunderlich Subject: [PATCH net 1/1] batman-adv: Avoid double-rtnl_lock ELP metric worker Date: Wed, 25 Feb 2026 09:46:14 +0100 Message-ID: <20260225084614.229077-2-sw@simonwunderlich.de> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260225084614.229077-1-sw@simonwunderlich.de> References: <20260225084614.229077-1-sw@simonwunderlich.de> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sven Eckelmann 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 --- net/batman-adv/bat_v_elp.c | 10 +++++++++- net/batman-adv/hard-interface.c | 8 ++++---- net/batman-adv/hard-interface.h | 1 + 3 files changed, 14 insertions(+), 5 deletions(-) diff --git a/net/batman-adv/bat_v_elp.c b/net/batman-adv/bat_v_elp.c index cb16c1ed2a58f..fe832093d421f 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; diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 5113f879736b5..1c488049d5546 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -204,7 +204,7 @@ static bool batadv_is_valid_iface(const struct net_device *net_dev) } /** - * batadv_get_real_netdevice() - check if the given netdev struct is a virtual + * __batadv_get_real_netdev() - check if the given netdev struct is a virtual * interface on top of another 'real' interface * @netdev: the device to check * @@ -214,7 +214,7 @@ static bool batadv_is_valid_iface(const struct net_device *net_dev) * Return: the 'real' net device or the original net device and NULL in case * of an error. */ -static struct net_device *batadv_get_real_netdevice(struct net_device *netdev) +struct net_device *__batadv_get_real_netdev(struct net_device *netdev) { struct batadv_hard_iface *hard_iface = NULL; struct net_device *real_netdev = NULL; @@ -267,7 +267,7 @@ struct net_device *batadv_get_real_netdev(struct net_device *net_device) struct net_device *real_netdev; rtnl_lock(); - real_netdev = batadv_get_real_netdevice(net_device); + real_netdev = __batadv_get_real_netdev(net_device); rtnl_unlock(); return real_netdev; @@ -336,7 +336,7 @@ static u32 batadv_wifi_flags_evaluate(struct net_device *net_device) if (batadv_is_cfg80211_netdev(net_device)) wifi_flags |= BATADV_HARDIF_WIFI_CFG80211_DIRECT; - real_netdev = batadv_get_real_netdevice(net_device); + real_netdev = __batadv_get_real_netdev(net_device); if (!real_netdev) return wifi_flags; diff --git a/net/batman-adv/hard-interface.h b/net/batman-adv/hard-interface.h index 9db8a310961ea..9ba8fb2bdceb4 100644 --- a/net/batman-adv/hard-interface.h +++ b/net/batman-adv/hard-interface.h @@ -67,6 +67,7 @@ enum batadv_hard_if_bcast { extern struct notifier_block batadv_hard_if_notifier; +struct net_device *__batadv_get_real_netdev(struct net_device *net_device); struct net_device *batadv_get_real_netdev(struct net_device *net_device); bool batadv_is_cfg80211_hardif(struct batadv_hard_iface *hard_iface); bool batadv_is_wifi_hardif(struct batadv_hard_iface *hard_iface); -- 2.47.3