From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Borkmann Subject: Re: [PATCH v2] cgroup: net_cls: fix false-positive "suspicious RCU usage" Date: Wed, 22 Jul 2015 13:56:44 +0200 Message-ID: <55AF84FC.2070502@iogearbox.net> References: <20150721164629.18385.14538.stgit@buzz> <20150722092320.30663.86742.stgit@buzz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20150722092320.30663.86742.stgit@buzz> Sender: linux-kernel-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Konstantin Khlebnikov Cc: netdev@vger.kernel.org, "David S. Miller" , Tejun Heo , cgroups@vger.kernel.org, Li Zefan , linux-kernel@vger.kernel.org On 07/22/2015 11:23 AM, Konstantin Khlebnikov wrote: > In dev_queue_xmit() net_cls protected with rcu-bh. ... > Signed-off-by: Konstantin Khlebnikov > --- > net/core/netclassid_cgroup.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/core/netclassid_cgroup.c b/net/core/netclassid_cgroup.c > index 1f2a126f4ffa..6441f47b1a8f 100644 > --- a/net/core/netclassid_cgroup.c > +++ b/net/core/netclassid_cgroup.c > @@ -23,7 +23,8 @@ static inline struct cgroup_cls_state *css_cls_state(struct cgroup_subsys_state > > struct cgroup_cls_state *task_cls_state(struct task_struct *p) > { > - return css_cls_state(task_css(p, net_cls_cgrp_id)); > + return css_cls_state(task_css_check(p, net_cls_cgrp_id, > + rcu_read_lock_bh_held())); Did you also check that after your patch this doesn't trigger on ingress either? There, this code path could be invoked under rcu_read_lock(). So, perhaps you need to check for both. > } > EXPORT_SYMBOL_GPL(task_cls_state);