From: Xin Long lucien.xin@gmail.com
[ Upstream commit 27d53323664c549b5bb2dfaaf6f7ad6e0376a64e ]
In the tx path of l2tp, l2tp_xmit_skb() calls skb_dst_set() to set skb's dst. However, it will eventually call inet6_csk_xmit() or ip_queue_xmit() where skb's dst will be overwritten by:
skb_dst_set_noref(skb, dst);
without releasing the old dst in skb. Then it causes dst/dev refcnt leak:
unregister_netdevice: waiting for eth0 to become free. Usage count = 1
This can be reproduced by simply running:
# modprobe l2tp_eth && modprobe l2tp_ip # sh ./tools/testing/selftests/net/l2tp.sh
So before going to inet6_csk_xmit() or ip_queue_xmit(), skb's dst should be dropped. This patch is to fix it by removing skb_dst_set() from l2tp_xmit_skb() and moving skb_dst_drop() into l2tp_xmit_core().
Fixes: 3557baabf280 ("[L2TP]: PPP over L2TP driver core") Reported-by: Hangbin Liu liuhangbin@gmail.com Signed-off-by: Xin Long lucien.xin@gmail.com Acked-by: James Chapman jchapman@katalix.com Tested-by: James Chapman jchapman@katalix.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/l2tp/l2tp_core.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
--- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -1134,6 +1134,7 @@ static int l2tp_xmit_core(struct l2tp_se
/* Queue the packet to IP for output */ skb->ignore_df = 1; + skb_dst_drop(skb); #if IS_ENABLED(CONFIG_IPV6) if (tunnel->sock->sk_family == PF_INET6 && !tunnel->v4mapped) error = inet6_csk_xmit(tunnel->sock, skb, NULL); @@ -1198,10 +1199,6 @@ int l2tp_xmit_skb(struct l2tp_session *s goto out_unlock; }
- /* Get routing info from the tunnel socket */ - skb_dst_drop(skb); - skb_dst_set(skb, sk_dst_check(sk, 0)); - inet = inet_sk(sk); fl = &inet->cork.fl; switch (tunnel->encap) {