ipv4: add a sock pointer to ip_queue_xmit()

ip_queue_xmit() assumes the skb it has to transmit is attached to an
inet socket. Commit 31c70d5956fc ("l2tp: keep original skb ownership")
changed l2tp to not change skb ownership and thus broke this assumption.

One fix is to add a new 'struct sock *sk' parameter to ip_queue_xmit(),
so that we do not assume skb->sk points to the socket used by l2tp
tunnel.

Fixes: 31c70d5956fc ("l2tp: keep original skb ownership")
Reported-by: Zhan Jianyu <nasa4836@gmail.com>
Tested-by: Zhan Jianyu <nasa4836@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 3 insertions, 3 deletions

diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 47f7a5490555..a4e37d7158dc 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -1131,10 +1131,10 @@ static int l2tp_xmit_core(struct l2tp_session *session, struct sk_buff *skb,
         skb->local_df = 1;
 #if IS_ENABLED(CONFIG_IPV6)
         if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped)
-                error = inet6_csk_xmit(skb, NULL);
+                error = inet6_csk_xmit(tunnel->sock, skb, NULL);
         else
 #endif
-                error = ip_queue_xmit(skb, fl);
+                error = ip_queue_xmit(tunnel->sock, skb, fl);
 
         /* Update stats */
         if (error >= 0) {
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 0b44d855269c..3397fe6897c0 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -487,7 +487,7 @@ static int l2tp_ip_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *m
 
 xmit:
         /* Queue the packet to IP for output */
-        rc = ip_queue_xmit(skb, &inet->cork.fl);
+        rc = ip_queue_xmit(sk, skb, &inet->cork.fl);
         rcu_read_unlock();
 
 error: