From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pablo Neira Ayuso Subject: Re: [patch net-next 3/6] net_sched: cls_bpf: remove faulty use of list_for_each_entry_rcu Date: Wed, 3 Dec 2014 14:50:48 +0100 Message-ID: <20141203135048.GA25676@salvia> References: <1417539636-12710-1-git-send-email-jiri@resnulli.us> <1417539636-12710-4-git-send-email-jiri@resnulli.us> <20141203121949.GA24370@salvia> <20141203132142.GG1860@nanopsycho.orion> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: netdev@vger.kernel.org, davem@davemloft.net, jhs@mojatatu.com To: Jiri Pirko Return-path: Received: from mail.us.es ([193.147.175.20]:38720 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752203AbaLCNse (ORCPT ); Wed, 3 Dec 2014 08:48:34 -0500 Content-Disposition: inline In-Reply-To: <20141203132142.GG1860@nanopsycho.orion> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Dec 03, 2014 at 02:21:42PM +0100, Jiri Pirko wrote: > Wed, Dec 03, 2014 at 01:19:49PM CET, pablo@netfilter.org wrote: > >On Tue, Dec 02, 2014 at 06:00:33PM +0100, 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; > >> 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) { > > > >We still need the _rcu here in the walk path. IIRC, this is called from the > >dump path and we hold no rtnl_lock there. > > It is called from tc_dump_tfilter only. And tc_dump_tfilter is always > called with rtnl_lock Right, nlk->cb_mutex is set to rtnl_lock so netlink_dump() grabs it for each recvmsg() invocation.