From mboxrd@z Thu Jan 1 00:00:00 1970 From: Shmulik Ladkani Subject: [PATCH] net: skbuff: Fix length validation in skb_vlan_pop() Date: Sun, 18 Sep 2016 13:09:18 +0300 Message-ID: <1474193358-20133-1-git-send-email-shmulik.ladkani@gmail.com> Cc: netdev@vger.kernel.org, Shmulik Ladkani To: Jiri Pirko , "David S . Miller" Return-path: Received: from mail-wm0-f68.google.com ([74.125.82.68]:33507 "EHLO mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755670AbcIRKJi (ORCPT ); Sun, 18 Sep 2016 06:09:38 -0400 Received: by mail-wm0-f68.google.com with SMTP id w84so3202272wmg.0 for ; Sun, 18 Sep 2016 03:09:37 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: In 93515d53b1 "net: move vlan pop/push functions into common code" skb_vlan_pop was moved from its private location in openvswitch to skbuff common code. In case !vlan_tx_tag_present, the original 'pop_vlan()' assured that skb->len is sufficient for the existence of a vlan_ethhdr (if skb->len < VLAN_ETH_HLEN then pop was a no-op). This validation was moved as is into the new common 'skb_vlan_pop'. Alas, in its original location (openvswitch), there's a guarantee that 'data' points to the mac_header, therefore the 'skb->len < VLAN_ETH_HLEN' condition made sense. However there's no such guarantee in the generic 'skb_vlan_pop'. For short packets received in rx path going through 'skb_vlan_pop', this causes 'skb_vlan_pop' to fail pop-ing a valid vlan hdr (in case tag is in payload), or to fail moving next tag into hw-accel tag. Instead, verify that 'skb->mac_len' is sufficient. Signed-off-by: Shmulik Ladkani --- Spotted by code review while doing work augmenting tc act vlan. net/core/skbuff.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 1e329d4112..cc2c004838 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4537,7 +4537,7 @@ int skb_vlan_pop(struct sk_buff *skb) } else { if (unlikely((skb->protocol != htons(ETH_P_8021Q) && skb->protocol != htons(ETH_P_8021AD)) || - skb->len < VLAN_ETH_HLEN)) + skb->mac_len < VLAN_ETH_HLEN)) return 0; err = __skb_vlan_pop(skb, &vlan_tci); @@ -4547,7 +4547,7 @@ int skb_vlan_pop(struct sk_buff *skb) /* move next vlan tag to hw accel tag */ if (likely((skb->protocol != htons(ETH_P_8021Q) && skb->protocol != htons(ETH_P_8021AD)) || - skb->len < VLAN_ETH_HLEN)) + skb->mac_len < VLAN_ETH_HLEN)) return 0; vlan_proto = skb->protocol; -- 2.7.4