From 55eff0eb7460c3d50716ed9eccf22257b046ca92 Mon Sep 17 00:00:00 2001 From: Miaohe Lin Date: Sat, 15 Aug 2020 04:44:31 -0400 Subject: [PATCH] net: Fix potential wrong skb->protocol in skb_vlan_untag() We may access the two bytes after vlan_hdr in vlan_set_encap_proto(). So we should pull VLAN_HLEN + sizeof(unsigned short) in skb_vlan_untag() or we may access the wrong data. Fixes: 0d5501c1c828 ("net: Always untag vlan-tagged traffic on input.") Signed-off-by: Miaohe Lin Signed-off-by: David S. Miller --- 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 7e2e502..5c3b906 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5418,8 +5418,8 @@ struct sk_buff *skb_vlan_untag(struct sk_buff *skb) skb = skb_share_check(skb, GFP_ATOMIC); if (unlikely(!skb)) goto err_free; - - if (unlikely(!pskb_may_pull(skb, VLAN_HLEN))) + /* We may access the two bytes after vlan_hdr in vlan_set_encap_proto(). */ + if (unlikely(!pskb_may_pull(skb, VLAN_HLEN + sizeof(unsigned short)))) goto err_free; vhdr = (struct vlan_hdr *)skb->data; -- 2.7.4