From mboxrd@z Thu Jan 1 00:00:00 1970 From: roy.qing.li@gmail.com Subject: [PATCH] ipv4: fix a potential use after free in gre_offload.c Date: Sat, 18 Oct 2014 17:26:04 +0800 Message-ID: <1413624364-12944-1-git-send-email-roy.qing.li@gmail.com> Cc: weichunc@plumgrid.com To: netdev@vger.kernel.org Return-path: Received: from mail-pa0-f44.google.com ([209.85.220.44]:56010 "EHLO mail-pa0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750860AbaJRJ0L (ORCPT ); Sat, 18 Oct 2014 05:26:11 -0400 Received: by mail-pa0-f44.google.com with SMTP id et14so2226035pad.17 for ; Sat, 18 Oct 2014 02:26:10 -0700 (PDT) Sender: netdev-owner@vger.kernel.org List-ID: From: Li RongQing pskb_may_pull() may change skb->data and make greh pointer oboslete; so need to reassign greh; but since first calling pskb_may_pull already ensured that skb->data has enough space for greh, so move the reference of greh before second calling pskb_may_pull(), to avoid reassign greh. Fixes: 7a7ffbabf9("ipv4: fix tunneled VM traffic over hw VXLAN/GRE GSO NIC") Cc: Wei-Chun Chao Signed-off-by: Li RongQing --- net/ipv4/gre_offload.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c index a777295..ccda096 100644 --- a/net/ipv4/gre_offload.c +++ b/net/ipv4/gre_offload.c @@ -55,13 +55,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb, if (csum) skb->encap_hdr_csum = 1; - if (unlikely(!pskb_may_pull(skb, ghl))) - goto out; - /* setup inner skb. */ skb->protocol = greh->protocol; skb->encapsulation = 0; + if (unlikely(!pskb_may_pull(skb, ghl))) + goto out; + __skb_pull(skb, ghl); skb_reset_mac_header(skb); skb_set_network_header(skb, skb_inner_network_offset(skb)); -- 1.7.10.4