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linux-next/net/l2tp
Guillaume Nault 8f7dc9ae4a l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6
Using l2tp_tunnel_find() in l2tp_ip_recv() is wrong for two reasons:

  * It doesn't take a reference on the returned tunnel, which makes the
    call racy wrt. concurrent tunnel deletion.

  * The lookup is only based on the tunnel identifier, so it can return
    a tunnel that doesn't match the packet's addresses or protocol.

For example, a packet sent to an L2TPv3 over IPv6 tunnel can be
delivered to an L2TPv2 over UDPv4 tunnel. This is worse than a simple
cross-talk: when delivering the packet to an L2TP over UDP tunnel, the
corresponding socket is UDP, where ->sk_backlog_rcv() is NULL. Calling
sk_receive_skb() will then crash the kernel by trying to execute this
callback.

And l2tp_tunnel_find() isn't even needed here. __l2tp_ip_bind_lookup()
properly checks the socket binding and connection settings. It was used
as a fallback mechanism for finding tunnels that didn't have their data
path registered yet. But it's not limited to this case and can be used
to replace l2tp_tunnel_find() in the general case.

Fix l2tp_ip6 in the same way.

Fixes: 0d76751fad ("l2tp: Add L2TPv3 IP encapsulation (no UDP) support")
Fixes: a32e0eec70 ("l2tp: introduce L2TPv3 IP encapsulation support for IPv6")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-11-05 22:22:15 +09:00
..
Kconfig l2tp: Call udp_sock_create 2014-07-14 16:12:15 -07:00
l2tp_core.c l2tp: fix race condition in l2tp_tunnel_delete 2017-09-26 10:24:34 -07:00
l2tp_core.h l2tp: fix race condition in l2tp_tunnel_delete 2017-09-26 10:24:34 -07:00
l2tp_debugfs.c net, l2tp: convert l2tp_tunnel.ref_count from atomic_t to refcount_t 2017-07-04 22:35:15 +01:00
l2tp_eth.c l2tp: fix l2tp_eth module loading 2017-10-01 22:35:07 -07:00
l2tp_ip6.c l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6 2017-11-05 22:22:15 +09:00
l2tp_ip.c l2tp: don't use l2tp_tunnel_find() in l2tp_ip and l2tp_ip6 2017-11-05 22:22:15 +09:00
l2tp_netlink.c l2tp: pass tunnel pointer to ->session_create() 2017-09-03 11:04:21 -07:00
l2tp_ppp.c l2tp: hold tunnel in pppol2tp_connect() 2017-10-31 10:59:52 +09:00
Makefile License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00