From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [PATCH net v2 2/2] lwtunnel: Fix oops on state free after encap module unload Date: Mon, 23 Jan 2017 15:42:48 -0500 (EST) Message-ID: <20170123.154248.261820530578170635.davem@davemloft.net> References: <1484753523-26230-1-git-send-email-rshearma@brocade.com> <1484958086-6151-1-git-send-email-rshearma@brocade.com> <1484958086-6151-3-git-send-email-rshearma@brocade.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: netdev@vger.kernel.org, tom@herbertland.com, roopa@cumulusnetworks.com, david.lebrun@uclouvain.be, tgraf@suug.ch, dsa@cumulusnetworks.com To: rshearma@brocade.com Return-path: Received: from shards.monkeyblade.net ([184.105.139.130]:56296 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750723AbdAWUmu (ORCPT ); Mon, 23 Jan 2017 15:42:50 -0500 In-Reply-To: <1484958086-6151-3-git-send-email-rshearma@brocade.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Robert Shearman Date: Sat, 21 Jan 2017 00:21:26 +0000 > @@ -115,8 +115,12 @@ int lwtunnel_build_state(struct net_device *dev, u16 encap_type, > ret = -EOPNOTSUPP; > rcu_read_lock(); Here 'ret' equals -EOPNOTSUPP > ops = rcu_dereference(lwtun_encaps[encap_type]); > - if (likely(ops && ops->build_state)) > - ret = ops->build_state(dev, encap, family, cfg, lws); > + if (likely(ops)) { > + if (likely(try_module_get(ops->owner) && ops->build_state)) > + ret = ops->build_state(dev, encap, family, cfg, lws); > + if (ret) > + module_put(ops->owner); If try_module_get() fails, 'ret' will still be -EOPNOTSUPP and we will module_put() on a module we did not grab a reference to. I think you need to adjust the logic here. You only want to 'put' if try_module_get() succeeds and ->build_state() returns an error.