[PATCH 4.8 28/45] geneve: avoid use-after-free of skb->data

From: Greg Kroah-Hartman
Date: Fri Dec 09 2016 - 11:22:24 EST


4.8-stable review patch. If anyone has any objections, please let me know.

------------------

From: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>


[ Upstream commit 5b01014759991887b1e450c9def01e58c02ab81b ]

geneve{,6}_build_skb can end up doing a pskb_expand_head(), which
makes the ip_hdr(skb) reference we stashed earlier stale. Since it's
only needed as an argument to ip_tunnel_ecn_encap(), move this
directly in the function call.

Fixes: 08399efc6319 ("geneve: ensure ECN info is handled properly in all tx/rx paths")
Signed-off-by: Sabrina Dubroca <sd@xxxxxxxxxxxxxxx>
Reviewed-by: John W. Linville <linville@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/net/geneve.c | 14 ++++----------
1 file changed, 4 insertions(+), 10 deletions(-)

--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -844,7 +844,6 @@ static netdev_tx_t geneve_xmit_skb(struc
struct geneve_dev *geneve = netdev_priv(dev);
struct geneve_sock *gs4 = geneve->sock4;
struct rtable *rt = NULL;
- const struct iphdr *iip; /* interior IP header */
int err = -EINVAL;
struct flowi4 fl4;
__u8 tos, ttl;
@@ -871,8 +870,6 @@ static netdev_tx_t geneve_xmit_skb(struc
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
skb_reset_mac_header(skb);

- iip = ip_hdr(skb);
-
if (info) {
const struct ip_tunnel_key *key = &info->key;
u8 *opts = NULL;
@@ -892,7 +889,7 @@ static netdev_tx_t geneve_xmit_skb(struc
if (unlikely(err))
goto tx_error;

- tos = ip_tunnel_ecn_encap(key->tos, iip, skb);
+ tos = ip_tunnel_ecn_encap(key->tos, ip_hdr(skb), skb);
ttl = key->ttl;
df = key->tun_flags & TUNNEL_DONT_FRAGMENT ? htons(IP_DF) : 0;
} else {
@@ -901,7 +898,7 @@ static netdev_tx_t geneve_xmit_skb(struc
if (unlikely(err))
goto tx_error;

- tos = ip_tunnel_ecn_encap(fl4.flowi4_tos, iip, skb);
+ tos = ip_tunnel_ecn_encap(fl4.flowi4_tos, ip_hdr(skb), skb);
ttl = geneve->ttl;
if (!ttl && IN_MULTICAST(ntohl(fl4.daddr)))
ttl = 1;
@@ -934,7 +931,6 @@ static netdev_tx_t geneve6_xmit_skb(stru
struct geneve_dev *geneve = netdev_priv(dev);
struct geneve_sock *gs6 = geneve->sock6;
struct dst_entry *dst = NULL;
- const struct iphdr *iip; /* interior IP header */
int err = -EINVAL;
struct flowi6 fl6;
__u8 prio, ttl;
@@ -959,8 +955,6 @@ static netdev_tx_t geneve6_xmit_skb(stru
sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
skb_reset_mac_header(skb);

- iip = ip_hdr(skb);
-
if (info) {
const struct ip_tunnel_key *key = &info->key;
u8 *opts = NULL;
@@ -981,7 +975,7 @@ static netdev_tx_t geneve6_xmit_skb(stru
if (unlikely(err))
goto tx_error;

- prio = ip_tunnel_ecn_encap(key->tos, iip, skb);
+ prio = ip_tunnel_ecn_encap(key->tos, ip_hdr(skb), skb);
ttl = key->ttl;
label = info->key.label;
} else {
@@ -991,7 +985,7 @@ static netdev_tx_t geneve6_xmit_skb(stru
goto tx_error;

prio = ip_tunnel_ecn_encap(ip6_tclass(fl6.flowlabel),
- iip, skb);
+ ip_hdr(skb), skb);
ttl = geneve->ttl;
if (!ttl && ipv6_addr_is_multicast(&fl6.daddr))
ttl = 1;