[ovs-dev,1/2] compat: ip6_gre: fix possible use-after-free in ip6erspan_rcv
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Message ID 1562685903-32115-1-git-send-email-gvrose8192@gmail.com
State New
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  • [ovs-dev,1/2] compat: ip6_gre: fix possible use-after-free in ip6erspan_rcv
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Commit Message

Gregory Rose July 9, 2019, 3:25 p.m. UTC
Upstream commit:
    commit 2a3cabae4536edbcb21d344e7aa8be7a584d2afb
    Author: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
    Date:   Sat Apr 6 17:16:53 2019 +0200

    net: ip6_gre: fix possible use-after-free in ip6erspan_rcv

    erspan_v6 tunnels run __iptunnel_pull_header on received skbs to remove
    erspan header. This can determine a possible use-after-free accessing
    pkt_md pointer in ip6erspan_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>

Fixes: c387d8177f20 ("compat: Add ipv6 GRE and IPV6 Tunneling")
Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: Greg Rose <gvrose8192@gmail.com>
---
 datapath/linux/compat/ip6_gre.c | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

Comments

William Tu July 9, 2019, 7:22 p.m. UTC | #1
On Tue, Jul 9, 2019 at 8:25 AM Greg Rose <gvrose8192@gmail.com> wrote:
>
> Upstream commit:
>     commit 2a3cabae4536edbcb21d344e7aa8be7a584d2afb
>     Author: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
>     Date:   Sat Apr 6 17:16:53 2019 +0200
>
>     net: ip6_gre: fix possible use-after-free in ip6erspan_rcv
>
>     erspan_v6 tunnels run __iptunnel_pull_header on received skbs to remove
>     erspan header. This can determine a possible use-after-free accessing
>     pkt_md pointer in ip6erspan_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>
>
> Fixes: c387d8177f20 ("compat: Add ipv6 GRE and IPV6 Tunneling")
> Cc: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
> Signed-off-by: Greg Rose <gvrose8192@gmail.com>
> ---

Thanks for backporting this patch.
Acked-by: William Tu <u9012063@gmail.com>

Patch
diff mbox series

diff --git a/datapath/linux/compat/ip6_gre.c b/datapath/linux/compat/ip6_gre.c
index a2cc45d..afff817 100644
--- a/datapath/linux/compat/ip6_gre.c
+++ b/datapath/linux/compat/ip6_gre.c
@@ -538,11 +538,11 @@  static int ip6gre_rcv(struct sk_buff *skb, const struct tnl_ptk_info *tpi)
 	return PACKET_RCVD;
 }
 
-static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
-			 struct tnl_ptk_info *tpi)
+static int ip6erspan_rcv(struct sk_buff *skb, 
+			 struct tnl_ptk_info *tpi,
+			 int gre_hdr_len)
 {
 	struct erspan_base_hdr *ershdr;
-	struct erspan_metadata *pkt_md;
 	const struct ipv6hdr *ipv6h;
 	struct erspan_md2 *md2;
 	struct ip6_tnl *tunnel;
@@ -566,17 +566,15 @@  static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
 		if (unlikely(!pskb_may_pull(skb, len)))
 			return PACKET_REJECT;
 
-		ershdr = (struct erspan_base_hdr *)skb->data;
-		pkt_md = (struct erspan_metadata *)(ershdr + 1);
-
 		if (__iptunnel_pull_header(skb, len,
 					   htons(ETH_P_TEB),
 					   false, false) < 0)
 			return PACKET_REJECT;
 
 		if (tunnel->parms.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;
 
@@ -589,6 +587,14 @@  static int ip6erspan_rcv(struct sk_buff *skb, int gre_hdr_len,
 			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));
 			info = &tun_dst->u.tun_info;
 			md = ip_tunnel_info_opts(info);
 			md->version = ver;
@@ -623,7 +629,7 @@  static int gre_rcv(struct sk_buff *skb)
 
 	if (unlikely(tpi.proto == htons(ETH_P_ERSPAN) ||
 		     tpi.proto == htons(ETH_P_ERSPAN2))) {
-		if (ip6erspan_rcv(skb, hdr_len, &tpi) == PACKET_RCVD)
+		if (ip6erspan_rcv(skb, &tpi, hdr_len) == PACKET_RCVD)
 			return 0;
 		goto out;
 	}