3.2.96-rc1 review patch. If anyone has any objections, please let me know.
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From: Guillaume Nault g.nault@alphalink.fr
commit f026bc29a8e093edfbb2a77700454b285c97e8ad upstream.
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: 309795f4bec2 ("l2tp: Add netlink control API for L2TP") Fixes: d9e31d17ceba ("l2tp: Add L2TP ethernet pseudowire support") Signed-off-by: Guillaume Nault g.nault@alphalink.fr Signed-off-by: David S. Miller davem@davemloft.net [bwh: Backported to 3.2: adjust context] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- net/l2tp/l2tp_core.h | 4 +++- net/l2tp/l2tp_eth.c | 11 +++-------- net/l2tp/l2tp_netlink.c | 8 ++++---- net/l2tp/l2tp_ppp.c | 19 +++++++------------ 4 files changed, 17 insertions(+), 25 deletions(-)
--- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -192,7 +192,9 @@ struct l2tp_tunnel { };
struct l2tp_nl_cmd_ops { - int (*session_create)(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg); + int (*session_create)(struct net *net, struct l2tp_tunnel *tunnel, + u32 session_id, u32 peer_session_id, + struct l2tp_session_cfg *cfg); int (*session_delete)(struct l2tp_session *session); };
--- a/net/l2tp/l2tp_eth.c +++ b/net/l2tp/l2tp_eth.c @@ -183,23 +183,18 @@ static void l2tp_eth_show(struct seq_fil } #endif
-static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg) +static int l2tp_eth_create(struct net *net, struct l2tp_tunnel *tunnel, + u32 session_id, u32 peer_session_id, + struct l2tp_session_cfg *cfg) { struct net_device *dev; char name[IFNAMSIZ]; - struct l2tp_tunnel *tunnel; struct l2tp_session *session; struct l2tp_eth *priv; struct l2tp_eth_sess *spriv; int rc; struct l2tp_eth_net *pn;
- tunnel = l2tp_tunnel_find(net, tunnel_id); - if (!tunnel) { - rc = -ENODEV; - goto out; - } - if (cfg->ifname) { dev = dev_get_by_name(net, cfg->ifname); if (dev) { --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -486,10 +486,10 @@ static int l2tp_nl_cmd_session_create(st break; }
- ret = -EPROTONOSUPPORT; - if (l2tp_nl_cmd_ops[cfg.pw_type]->session_create) - ret = (*l2tp_nl_cmd_ops[cfg.pw_type]->session_create)(net, tunnel_id, - session_id, peer_session_id, &cfg); + ret = l2tp_nl_cmd_ops[cfg.pw_type]->session_create(net, tunnel, + session_id, + peer_session_id, + &cfg);
out_tunnel: l2tp_tunnel_dec_refcount(tunnel); --- a/net/l2tp/l2tp_ppp.c +++ b/net/l2tp/l2tp_ppp.c @@ -825,25 +825,20 @@ end:
#ifdef CONFIG_L2TP_V3
-/* Called when creating sessions via the netlink interface. - */ -static int pppol2tp_session_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg) +/* Called when creating sessions via the netlink interface. */ +static int pppol2tp_session_create(struct net *net, struct l2tp_tunnel *tunnel, + u32 session_id, u32 peer_session_id, + struct l2tp_session_cfg *cfg) { int error; - struct l2tp_tunnel *tunnel; struct l2tp_session *session; struct pppol2tp_session *ps;
- tunnel = l2tp_tunnel_find(net, tunnel_id); - - /* Error if we can't find the tunnel */ - error = -ENOENT; - if (tunnel == NULL) - goto out; - /* Error if tunnel socket is not prepped */ - if (tunnel->sock == NULL) + if (!tunnel->sock) { + error = -ENOENT; goto out; + }
/* Default MTU values. */ if (cfg->mtu == 0)