From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jamal Hadi Salim Subject: Re: [patch net-next 3/6] net_sched: cls_bpf: remove faulty use of list_for_each_entry_rcu Date: Wed, 03 Dec 2014 07:51:15 -0500 Message-ID: <547F0743.4040301@mojatatu.com> References: <1417539636-12710-1-git-send-email-jiri@resnulli.us> <1417539636-12710-4-git-send-email-jiri@resnulli.us> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: davem@davemloft.net To: Jiri Pirko , netdev@vger.kernel.org Return-path: Received: from mail-ig0-f178.google.com ([209.85.213.178]:52961 "EHLO mail-ig0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750833AbaLCMvR (ORCPT ); Wed, 3 Dec 2014 07:51:17 -0500 Received: by mail-ig0-f178.google.com with SMTP id hl2so12650082igb.17 for ; Wed, 03 Dec 2014 04:51:17 -0800 (PST) In-Reply-To: <1417539636-12710-4-git-send-email-jiri@resnulli.us> Sender: netdev-owner@vger.kernel.org List-ID: On 12/02/14 12:00, Jiri Pirko wrote: > rcu variant is not correct here. The code is called by updater (rtnl > lock is held), not by reader (no rcu_read_lock is held). > > Signed-off-by: Jiri Pirko > --- > net/sched/cls_bpf.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c > index cbfaf6f..d0de979 100644 > --- a/net/sched/cls_bpf.c > +++ b/net/sched/cls_bpf.c > @@ -141,7 +141,7 @@ static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle) > if (head == NULL) > return 0UL; > > - list_for_each_entry_rcu(prog, &head->plist, link) { > + list_for_each_entry(prog, &head->plist, link) { > if (prog->handle == handle) { > ret = (unsigned long) prog; The above is ok i think - only one user space entrant at a time and datapath is not affected because no modification is happening. > break; > @@ -337,7 +337,7 @@ static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg) > struct cls_bpf_head *head = rtnl_dereference(tp->root); > struct cls_bpf_prog *prog; > > - list_for_each_entry_rcu(prog, &head->plist, link) { > + list_for_each_entry(prog, &head->plist, link) { > if (arg->count < arg->skip) > goto skip; > if (arg->fn(tp, (unsigned long) prog, arg) < 0) { > I think this may be problematic. Doesnt a flush operation also use the walker? cheers, jamal