From f39acc84aad10710e89835c60d3b6694c43a8dd9 Mon Sep 17 00:00:00 2001 From: Shmulik Ladkani Date: Thu, 29 Sep 2016 12:10:40 +0300 Subject: [PATCH] net/sched: act_vlan: Push skb->data to mac_header prior calling skb_vlan_*() functions 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 Signed-off-by: David S. Miller --- 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 a95c00b119da..b57fcbcefea1 100644 --- a/net/sched/act_vlan.c +++ b/net/sched/act_vlan.c @@ -37,6 +37,12 @@ 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); @@ -83,6 +89,9 @@ 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; } -- 2.20.1