linux-kernel - [PATCH v2 2/2] ip6_tunnel: fix potential issue in __ip6_tnl

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Message-Id: <1496883476-17445-2-git-send-email-yanhaishuang@cmss.chinamobile.com>
Date:   Thu,  8 Jun 2017 08:57:56 +0800
From:   Haishuang Yan <yanhaishuang@...s.chinamobile.com>
To:     "=David S. Miller" <davem@...emloft.net>,
        Alexey Kuznetsov <kuznet@....inr.ac.ru>,
        James Morris <jmorris@...ei.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Patrick McHardy <kaber@...sh.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Haishuang Yan <yanhaishuang@...s.chinamobile.com>,
        Alexei Starovoitov <ast@...com>
Subject: [PATCH v2 2/2] ip6_tunnel: fix potential issue in __ip6_tnl_rcv

When __ip6_tnl_rcv fails, the tun_dst won't be freed, so move
skb_dst_set to begin and tun_dst would be freed by kfree_skb.

CC: Alexei Starovoitov <ast@...com>
Fixes: 8d79266bc48c ("ip6_tunnel: add collect_md mode to IPv6 tunnels")
Signed-off-by: Haishuang Yan <yanhaishuang@...s.chinamobile.com>
---
 net/ipv6/ip6_tunnel.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/ip6_tunnel.c b/net/ipv6/ip6_tunnel.c
index 9b37f97..bf45f1b 100644
--- a/net/ipv6/ip6_tunnel.c
+++ b/net/ipv6/ip6_tunnel.c
@@ -789,6 +789,9 @@ static int __ip6_tnl_rcv(struct ip6_tnl *tunnel, struct sk_buff *skb,
 	const struct ipv6hdr *ipv6h = ipv6_hdr(skb);
 	int err;
 
+	if (tun_dst)
+		skb_dst_set(skb, (struct dst_entry *)tun_dst);
+
 	if ((!(tpi->flags & TUNNEL_CSUM) &&
 	     (tunnel->parms.i_flags & TUNNEL_CSUM)) ||
 	    ((tpi->flags & TUNNEL_CSUM) &&
@@ -852,9 +855,6 @@ static int __ip6_tnl_rcv(struct ip6_tnl *tunnel, struct sk_buff *skb,
 
 	skb_scrub_packet(skb, !net_eq(tunnel->net, dev_net(tunnel->dev)));
 
-	if (tun_dst)
-		skb_dst_set(skb, (struct dst_entry *)tun_dst);
-
 	gro_cells_receive(&tunnel->gro_cells, skb);
 	return 0;
 
-- 
1.8.3.1