From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jiri Pirko , Roman Kapl , "David S. Miller" , Cong Wang Subject: [PATCH 4.14 112/115] net: sched: fix crash when deleting secondary chains Date: Fri, 2 Mar 2018 09:51:55 +0100 Message-Id: <20180302084508.373570078@linuxfoundation.org> In-Reply-To: <20180302084503.856536800@linuxfoundation.org> References: <20180302084503.856536800@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Roman Kapl commit d7aa04a5e82b4f254d306926c81eae8df69e5200 upstream. If you flush (delete) a filter chain other than chain 0 (such as when deleting the device), the kernel may run into a use-after-free. The chain refcount must not be decremented unless we are sure we are done with the chain. To reproduce the bug, run: ip link add dtest type dummy tc qdisc add dev dtest ingress tc filter add dev dtest chain 1 parent ffff: flower ip link del dtest Introduced in: commit f93e1cdcf42c ("net/sched: fix filter flushing"), but unless you have KAsan or luck, you won't notice it until commit 0dadc117ac8b ("cls_flower: use tcf_exts_get_net() before call_rcu()") Fixes: f93e1cdcf42c ("net/sched: fix filter flushing") Acked-by: Jiri Pirko Signed-off-by: Roman Kapl Signed-off-by: David S. Miller Cc: Cong Wang Signed-off-by: Greg Kroah-Hartman --- net/sched/cls_api.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) --- a/net/sched/cls_api.c +++ b/net/sched/cls_api.c @@ -197,14 +197,15 @@ static struct tcf_chain *tcf_chain_creat static void tcf_chain_flush(struct tcf_chain *chain) { - struct tcf_proto *tp; + struct tcf_proto *tp = rtnl_dereference(chain->filter_chain); if (chain->p_filter_chain) RCU_INIT_POINTER(*chain->p_filter_chain, NULL); - while ((tp = rtnl_dereference(chain->filter_chain)) != NULL) { + while (tp) { RCU_INIT_POINTER(chain->filter_chain, tp->next); - tcf_chain_put(chain); tcf_proto_destroy(tp); + tp = rtnl_dereference(chain->filter_chain); + tcf_chain_put(chain); } }