[PPPOL2TP]: Fix use-after-free

Don't use skb->len after passing it to ip_queue_xmit.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/net/pppol2tp.c b/drivers/net/pppol2tp.c
index 5891a0fbdc8b..856610f0624e 100644
--- a/drivers/net/pppol2tp.c
+++ b/drivers/net/pppol2tp.c
@@ -824,6 +824,7 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
         struct pppol2tp_session *session;
         struct pppol2tp_tunnel *tunnel;
         struct udphdr *uh;
+        unsigned int len;
 
         error = -ENOTCONN;
         if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
@@ -912,14 +913,15 @@ static int pppol2tp_sendmsg(struct kiocb *iocb, struct socket *sock, struct msgh
         }
 
         /* Queue the packet to IP for output */
+        len = skb->len;
         error = ip_queue_xmit(skb, 1);
 
         /* Update stats */
         if (error >= 0) {
                 tunnel->stats.tx_packets++;
-                tunnel->stats.tx_bytes += skb->len;
+                tunnel->stats.tx_bytes += len;
                 session->stats.tx_packets++;
-                session->stats.tx_bytes += skb->len;
+                session->stats.tx_bytes += len;
         } else {
                 tunnel->stats.tx_errors++;
                 session->stats.tx_errors++;
@@ -958,6 +960,7 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
         __wsum csum = 0;
         struct sk_buff *skb2 = NULL;
         struct udphdr *uh;
+        unsigned int len;
 
         if (sock_flag(sk, SOCK_DEAD) || !(sk->sk_state & PPPOX_CONNECTED))
                 goto abort;
@@ -1050,14 +1053,15 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
         skb2->dst = sk_dst_get(sk_tun);
 
         /* Queue the packet to IP for output */
+        len = skb2->len;
         rc = ip_queue_xmit(skb2, 1);
 
         /* Update stats */
         if (rc >= 0) {
                 tunnel->stats.tx_packets++;
-                tunnel->stats.tx_bytes += skb2->len;
+                tunnel->stats.tx_bytes += len;
                 session->stats.tx_packets++;
-                session->stats.tx_bytes += skb2->len;
+                session->stats.tx_bytes += len;
         } else {
                 tunnel->stats.tx_errors++;
                 session->stats.tx_errors++;