From: Shmulik Ladkani Date: Tue, 20 Sep 2016 09:48:36 +0000 (+0300) Subject: net: skbuff: Remove errornous length validation in skb_vlan_pop() X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=636c2628086e40c86dac7ddc84a1c4b4fcccc6e3;p=GitHub%2Fmoto-9609%2Fandroid_kernel_motorola_exynos9610.git net: skbuff: Remove errornous length validation in skb_vlan_pop() 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 skb has non hw-accel vlan tag, the original 'pop_vlan()' assured that skb->len is sufficient (if skb->len < VLAN_ETH_HLEN then pop was considered a no-op). This validation was moved as is into the new common 'skb_vlan_pop'. Alas, in its original location (openvswitch), there was 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 the non hw-accel case) or to fail moving next tag into hw-accel tag. Remove the 'skb->len < VLAN_ETH_HLEN' condition entirely: It is superfluous since inner '__skb_vlan_pop' already verifies there are VLAN_ETH_HLEN writable bytes at the mac_header. Note this presents a slight change to skb_vlan_pop() users: In case total length is smaller than VLAN_ETH_HLEN, skb_vlan_pop() now returns an error, as opposed to previous "no-op" behavior. Existing callers (e.g. tc act vlan, ovs) usually drop the packet if 'skb_vlan_pop' fails. Fixes: 93515d53b1 ("net: move vlan pop/push functions into common code") Signed-off-by: Shmulik Ladkani Cc: Pravin Shelar Reviewed-by: Pravin B Shelar Signed-off-by: David S. Miller --- diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 6c22351bd519..b2a51bf1b0f9 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -4567,9 +4567,8 @@ int skb_vlan_pop(struct sk_buff *skb) if (likely(skb_vlan_tag_present(skb))) { skb->vlan_tci = 0; } else { - if (unlikely((skb->protocol != htons(ETH_P_8021Q) && - skb->protocol != htons(ETH_P_8021AD)) || - skb->len < VLAN_ETH_HLEN)) + if (unlikely(skb->protocol != htons(ETH_P_8021Q) && + skb->protocol != htons(ETH_P_8021AD))) return 0; err = __skb_vlan_pop(skb, &vlan_tci); @@ -4577,9 +4576,8 @@ int skb_vlan_pop(struct sk_buff *skb) return err; } /* 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)) + if (likely(skb->protocol != htons(ETH_P_8021Q) && + skb->protocol != htons(ETH_P_8021AD))) return 0; vlan_proto = skb->protocol;