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Xin Long 73e42f4d2d l2tp: remove skb_dst_set() from l2tp_xmit_skb() 
[ Upstream commit 27d5332366 ]

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: 3557baabf2 ("[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>
 		2020-07-22 09:32:47 +02:00
..
Kconfig treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
l2tp_core.c l2tp: remove skb_dst_set() from l2tp_xmit_skb() 2020-07-22 09:32:47 +02:00
l2tp_core.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
l2tp_debugfs.c l2tp: no need to check return value of debugfs_create functions 2019-06-14 08:45:05 -07:00
l2tp_eth.c net: core: add generic lockdep keys 2019-10-24 14:53:48 -07:00
l2tp_ip.c l2tp: do not use inet_hash()/inet_unhash() 2020-06-10 20:24:54 +02:00
l2tp_ip6.c l2tp: do not use inet_hash()/inet_unhash() 2020-06-10 20:24:54 +02:00
l2tp_netlink.c l2tp: Allow management of tunnels and session in user namespace 2020-04-21 09:04:44 +02:00
l2tp_ppp.c compat_ioctl: pppoe: fix PPPOEIOCSFWD handling 2019-07-30 14:42:13 -07:00