From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiri Pirko Subject: Re: [PATCH net-next] net/sched: cls_flower: verify root pointer before dereferncing it Date: Tue, 22 Nov 2016 15:48:44 +0100 Message-ID: <20161122144844.GB1819@nanopsycho> References: <1479824726-62607-1-git-send-email-roid@mellanox.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: "David S. Miller" , netdev@vger.kernel.org, Jiri Pirko , Cong Wang , Or Gerlitz , Cong Wang To: Roi Dayan Return-path: Received: from mail-qk0-f195.google.com ([209.85.220.195]:35563 "EHLO mail-qk0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755421AbcKVPGB (ORCPT ); Tue, 22 Nov 2016 10:06:01 -0500 Received: by mail-qk0-f195.google.com with SMTP id n204so4466756qke.2 for ; Tue, 22 Nov 2016 07:06:00 -0800 (PST) Content-Disposition: inline In-Reply-To: <1479824726-62607-1-git-send-email-roid@mellanox.com> Sender: netdev-owner@vger.kernel.org List-ID: Tue, Nov 22, 2016 at 03:25:26PM CET, roid@mellanox.com wrote: >tp->root is being allocated in init() time and kfreed in destroy() >however it is being dereferenced in classify() path. > >We could be in classify() path after destroy() was called and thus >tp->root is null. Verifying if tp->root is null in classify() path >is enough because it's being freed with kfree_rcu() and classify() >path is under rcu_read_lock(). > >Fixes: 1e052be69d04 ("net_sched: destroy proto tp when all filters are gone") >Signed-off-by: Roi Dayan >Cc: Cong Wang This is correct Reviewed-by: Jiri Pirko The other way to fix this would be to move tp->ops->destroy call to call_rcu phase. That would require bigger changes though. net-next perhaps? >--- > >Hi Cong, all > >As stated above, the issue was introduced with commit 1e052be69d04 ("net_sched: destroy >proto tp when all filters are gone"). This patch provides a fix only for cls_flower where >I succeeded in reproducing the issue. Cong, if you can/want to come up with a fix that >will be applicable for all the others classifiners, I am fine with that. > >Thanks, >Roi > > > net/sched/cls_flower.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > >diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c >index e8dd09a..88a26c4 100644 >--- a/net/sched/cls_flower.c >+++ b/net/sched/cls_flower.c >@@ -135,7 +135,7 @@ static int fl_classify(struct sk_buff *skb, const struct tcf_proto *tp, > struct fl_flow_key skb_mkey; > struct ip_tunnel_info *info; > >- if (!atomic_read(&head->ht.nelems)) >+ if (!head || !atomic_read(&head->ht.nelems)) > return -1; > > fl_clear_masked_range(&skb_key, &head->mask); >-- >2.7.4 >