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authorLorenzo Bianconi <lorenzo.bianconi@redhat.com>2019-04-06 17:16:52 +0200
committerDavid S. Miller <davem@davemloft.net>2019-04-08 16:16:47 -0700
commit492b67e28ee5f2a2522fb72e3d3bcb990e461514 (patch)
tree02486e4add5ae9176d978eeacc6463f5c52e9897
parentb75bb8a5b755d0c7bf1ac071e4df2349a7644a1e (diff)
download96b-common-492b67e28ee5f2a2522fb72e3d3bcb990e461514.tar.gz
net: ip_gre: fix possible use-after-free in erspan_rcv
erspan tunnels run __iptunnel_pull_header on received skbs to remove gre and erspan headers. This can determine a possible use-after-free accessing pkt_md pointer in erspan_rcv since the packet will be 'uncloned' running pskb_expand_head if it is a cloned gso skb (e.g if the packet has been sent though a veth device). Fix it resetting pkt_md pointer after __iptunnel_pull_header Fixes: 1d7e2ed22f8d ("net: erspan: refactor existing erspan code") Signed-off-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--net/ipv4/ip_gre.c15
1 files changed, 10 insertions, 5 deletions
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index fd219f7bd3ea..4b0526441476 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -259,7 +259,6 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
struct net *net = dev_net(skb->dev);
struct metadata_dst *tun_dst = NULL;
struct erspan_base_hdr *ershdr;
- struct erspan_metadata *pkt_md;
struct ip_tunnel_net *itn;
struct ip_tunnel *tunnel;
const struct iphdr *iph;
@@ -282,9 +281,6 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
if (unlikely(!pskb_may_pull(skb, len)))
return PACKET_REJECT;
- ershdr = (struct erspan_base_hdr *)(skb->data + gre_hdr_len);
- pkt_md = (struct erspan_metadata *)(ershdr + 1);
-
if (__iptunnel_pull_header(skb,
len,
htons(ETH_P_TEB),
@@ -292,8 +288,9 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
goto drop;
if (tunnel->collect_md) {
+ struct erspan_metadata *pkt_md, *md;
struct ip_tunnel_info *info;
- struct erspan_metadata *md;
+ unsigned char *gh;
__be64 tun_id;
__be16 flags;
@@ -306,6 +303,14 @@ static int erspan_rcv(struct sk_buff *skb, struct tnl_ptk_info *tpi,
if (!tun_dst)
return PACKET_REJECT;
+ /* skb can be uncloned in __iptunnel_pull_header, so
+ * old pkt_md is no longer valid and we need to reset
+ * it
+ */
+ gh = skb_network_header(skb) +
+ skb_network_header_len(skb);
+ pkt_md = (struct erspan_metadata *)(gh + gre_hdr_len +
+ sizeof(*ershdr));
md = ip_tunnel_info_opts(&tun_dst->u.tun_info);
md->version = ver;
md2 = &md->u.md2;