linux/net/l2tp
Guillaume Nault f026bc29a8 l2tp: pass tunnel pointer to ->session_create()
Using l2tp_tunnel_find() in pppol2tp_session_create() and
l2tp_eth_create() is racy, because no reference is held on the
returned session. These functions are only used to implement the
->session_create callback which is run by l2tp_nl_cmd_session_create().
Therefore searching for the parent tunnel isn't necessary because
l2tp_nl_cmd_session_create() already has a pointer to it and holds a
reference.

This patch modifies ->session_create()'s prototype to directly pass the
the parent tunnel as parameter, thus avoiding searching for it in
pppol2tp_session_create() and l2tp_eth_create().

Since we have to touch the ->session_create() call in
l2tp_nl_cmd_session_create(), let's also remove the useless conditional:
we know that ->session_create isn't NULL at this point because it's
already been checked earlier in this same function.

Finally, one might be tempted to think that the removed
l2tp_tunnel_find() calls were harmless because they would return the
same tunnel as the one held by l2tp_nl_cmd_session_create() anyway.
But that tunnel might be removed and a new one created with same tunnel
Id before the l2tp_tunnel_find() call. In this case l2tp_tunnel_find()
would return the new tunnel which wouldn't be protected by the
reference held by l2tp_nl_cmd_session_create().

Fixes: 309795f4be ("l2tp: Add netlink control API for L2TP")
Fixes: d9e31d17ce ("l2tp: Add L2TP ethernet pseudowire support")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
2017-09-03 11:04:21 -07:00
..
Kconfig l2tp: Call udp_sock_create 2014-07-14 16:12:15 -07:00
Makefile l2tp: introduce L2TPv3 IP encapsulation support for IPv6 2012-05-01 09:30:55 -04:00
l2tp_core.c l2tp: prevent creation of sessions on terminated tunnels 2017-09-03 11:04:21 -07:00
l2tp_core.h l2tp: pass tunnel pointer to ->session_create() 2017-09-03 11:04:21 -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: pass tunnel pointer to ->session_create() 2017-09-03 11:04:21 -07:00
l2tp_ip.c l2tp: fix race in l2tp_recv_common() 2017-04-01 20:16:41 -07:00
l2tp_ip6.c l2tp: fix race in l2tp_recv_common() 2017-04-01 20:16:41 -07:00
l2tp_netlink.c l2tp: pass tunnel pointer to ->session_create() 2017-09-03 11:04:21 -07:00
l2tp_ppp.c l2tp: pass tunnel pointer to ->session_create() 2017-09-03 11:04:21 -07:00