From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shmulik Ladkani Subject: [PATCH v3 net 1/2] net/sched: act_vlan: Push skb->data to mac_header prior calling skb_vlan_*() functions Date: Thu, 29 Sep 2016 12:10:40 +0300 Message-ID: <1475140241-23586-1-git-send-email-shmulik.ladkani@gmail.com> Cc: netdev@vger.kernel.org, Jamal Hadi Salim , Shmulik Ladkani , Daniel Borkmann , Pravin Shelar , Jiri Pirko To: "David S . Miller" Return-path: Received: from mail-wm0-f67.google.com ([74.125.82.67]:34065 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933488AbcI2JLI (ORCPT ); Thu, 29 Sep 2016 05:11:08 -0400 Received: by mail-wm0-f67.google.com with SMTP id w72so1053833wmf.1 for ; Thu, 29 Sep 2016 02:11:08 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: Generic skb_vlan_push/skb_vlan_pop functions don't properly handle the case where the input skb data pointer does not point at the mac header: - They're doing push/pop, but fail to properly unwind data back to its original location. For example, in the skb_vlan_push case, any subsequent 'skb_push(skb, skb->mac_len)' calls make the skb->data point 4 bytes BEFORE start of frame, leading to bogus frames that may be transmitted. - They update rcsum per the added/removed 4 bytes tag. Alas if data is originally after the vlan/eth headers, then these bytes were already pulled out of the csum. OTOH calling skb_vlan_push/skb_vlan_pop with skb->data at mac_header present no issues. act_vlan is the only caller to skb_vlan_*() that has skb->data pointing at network header (upon ingress). Other calles (ovs, bpf) already adjust skb->data at mac_header. This patch fixes act_vlan to point to the mac_header prior calling skb_vlan_*() functions, as other callers do. Signed-off-by: Shmulik Ladkani Cc: Daniel Borkmann Cc: Pravin Shelar Cc: Jiri Pirko --- net/sched/act_vlan.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/net/sched/act_vlan.c b/net/sched/act_vlan.c index 691409de3e..4ffc6c13a5 100644 --- a/net/sched/act_vlan.c +++ b/net/sched/act_vlan.c @@ -36,6 +36,12 @@ static int tcf_vlan(struct sk_buff *skb, const struct tc_action *a, bstats_update(&v->tcf_bstats, skb); action = v->tcf_action; + /* Ensure 'data' points at mac_header prior calling vlan manipulating + * functions. + */ + if (skb_at_tc_ingress(skb)) + skb_push_rcsum(skb, skb->mac_len); + switch (v->tcfv_action) { case TCA_VLAN_ACT_POP: err = skb_vlan_pop(skb); @@ -57,6 +63,9 @@ drop: action = TC_ACT_SHOT; v->tcf_qstats.drops++; unlock: + if (skb_at_tc_ingress(skb)) + skb_pull_rcsum(skb, skb->mac_len); + spin_unlock(&v->tcf_lock); return action; } -- 2.7.4