| From foo@baz Fri 17 Jul 2020 11:04:44 AM CEST |
| From: Xin Long <lucien.xin@gmail.com> |
| Date: Tue, 7 Jul 2020 02:02:32 +0800 |
| Subject: l2tp: remove skb_dst_set() from l2tp_xmit_skb() |
| |
| 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) { |
