From: Guillaume Nault g.nault@alphalink.fr
commit 2777e2ab5a9cf2b4524486c6db1517a6ded25261 upstream.
Callers of l2tp_nl_session_find() need to hold a reference on the returned session since there's no guarantee that it isn't going to disappear from under them.
Relying on the fact that no l2tp netlink message may be processed concurrently isn't enough: sessions can be deleted by other means (e.g. by closing the PPPOL2TP socket of a ppp pseudowire).
l2tp_nl_cmd_session_delete() is a bit special: it runs a callback function that may require a previous call to session->ref(). In particular, for ppp pseudowires, the callback is l2tp_session_delete(), which then calls pppol2tp_session_close() and dereferences the PPPOL2TP socket. The socket might already be gone at the moment l2tp_session_delete() calls session->ref(), so we need to take a reference during the session lookup. So we need to pass the do_ref variable down to l2tp_session_get() and l2tp_session_get_by_ifname().
Since all callers have to be updated, l2tp_session_find_by_ifname() and l2tp_nl_session_find() are renamed to reflect their new behaviour.
Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP") Signed-off-by: Guillaume Nault g.nault@alphalink.fr Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Amit Pundir amit.pundir@linaro.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Giuliano Procida gprocida@google.com --- net/l2tp/l2tp_core.c | 9 +++++++-- net/l2tp/l2tp_core.h | 3 ++- net/l2tp/l2tp_netlink.c | 39 ++++++++++++++++++++++++++------------- 3 files changed, 35 insertions(+), 16 deletions(-)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index 8cbccddc0b1e..08377af93552 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -355,7 +355,8 @@ EXPORT_SYMBOL_GPL(l2tp_session_get_nth); /* Lookup a session by interface name. * This is very inefficient but is only used by management interfaces. */ -struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname) +struct l2tp_session *l2tp_session_get_by_ifname(struct net *net, char *ifname, + bool do_ref) { struct l2tp_net *pn = l2tp_pernet(net); int hash; @@ -365,7 +366,11 @@ struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname) for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) { hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) { if (!strcmp(session->ifname, ifname)) { + l2tp_session_inc_refcount(session); + if (do_ref && session->ref) + session->ref(session); rcu_read_unlock_bh(); + return session; } } @@ -375,7 +380,7 @@ struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname)
return NULL; } -EXPORT_SYMBOL_GPL(l2tp_session_find_by_ifname); +EXPORT_SYMBOL_GPL(l2tp_session_get_by_ifname);
static int l2tp_session_add_to_tunnel(struct l2tp_tunnel *tunnel, struct l2tp_session *session) diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index 06323a12d62c..ee59d9961d1f 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -252,7 +252,8 @@ struct l2tp_session *l2tp_session_find(struct net *net, u32 session_id); struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth, bool do_ref); -struct l2tp_session *l2tp_session_find_by_ifname(struct net *net, char *ifname); +struct l2tp_session *l2tp_session_get_by_ifname(struct net *net, char *ifname, + bool do_ref); struct l2tp_tunnel *l2tp_tunnel_find(struct net *net, u32 tunnel_id); struct l2tp_tunnel *l2tp_tunnel_find_nth(struct net *net, int nth);
diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index 43f0af1c4697..63a2430ff40a 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -55,7 +55,8 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, /* Accessed under genl lock */ static const struct l2tp_nl_cmd_ops *l2tp_nl_cmd_ops[__L2TP_PWTYPE_MAX];
-static struct l2tp_session *l2tp_nl_session_find(struct genl_info *info) +static struct l2tp_session *l2tp_nl_session_get(struct genl_info *info, + bool do_ref) { u32 tunnel_id; u32 session_id; @@ -66,14 +67,15 @@ static struct l2tp_session *l2tp_nl_session_find(struct genl_info *info)
if (info->attrs[L2TP_ATTR_IFNAME]) { ifname = nla_data(info->attrs[L2TP_ATTR_IFNAME]); - session = l2tp_session_find_by_ifname(net, ifname); + session = l2tp_session_get_by_ifname(net, ifname, do_ref); } else if ((info->attrs[L2TP_ATTR_SESSION_ID]) && (info->attrs[L2TP_ATTR_CONN_ID])) { tunnel_id = nla_get_u32(info->attrs[L2TP_ATTR_CONN_ID]); session_id = nla_get_u32(info->attrs[L2TP_ATTR_SESSION_ID]); tunnel = l2tp_tunnel_find(net, tunnel_id); if (tunnel) - session = l2tp_session_find(net, tunnel, session_id); + session = l2tp_session_get(net, tunnel, session_id, + do_ref); }
return session; @@ -644,7 +646,7 @@ static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *inf struct l2tp_session *session; u16 pw_type;
- session = l2tp_nl_session_find(info); + session = l2tp_nl_session_get(info, true); if (session == NULL) { ret = -ENODEV; goto out; @@ -658,6 +660,10 @@ static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *inf if (l2tp_nl_cmd_ops[pw_type] && l2tp_nl_cmd_ops[pw_type]->session_delete) ret = (*l2tp_nl_cmd_ops[pw_type]->session_delete)(session);
+ if (session->deref) + session->deref(session); + l2tp_session_dec_refcount(session); + out: return ret; } @@ -667,7 +673,7 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf int ret = 0; struct l2tp_session *session;
- session = l2tp_nl_session_find(info); + session = l2tp_nl_session_get(info, false); if (session == NULL) { ret = -ENODEV; goto out; @@ -702,6 +708,8 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf ret = l2tp_session_notify(&l2tp_nl_family, info, session, L2TP_CMD_SESSION_MODIFY);
+ l2tp_session_dec_refcount(session); + out: return ret; } @@ -788,29 +796,34 @@ static int l2tp_nl_cmd_session_get(struct sk_buff *skb, struct genl_info *info) struct sk_buff *msg; int ret;
- session = l2tp_nl_session_find(info); + session = l2tp_nl_session_get(info, false); if (session == NULL) { ret = -ENODEV; - goto out; + goto err; }
msg = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL); if (!msg) { ret = -ENOMEM; - goto out; + goto err_ref; }
ret = l2tp_nl_session_send(msg, info->snd_portid, info->snd_seq, 0, session, L2TP_CMD_SESSION_GET); if (ret < 0) - goto err_out; + goto err_ref_msg;
- return genlmsg_unicast(genl_info_net(info), msg, info->snd_portid); + ret = genlmsg_unicast(genl_info_net(info), msg, info->snd_portid);
-err_out: - nlmsg_free(msg); + l2tp_session_dec_refcount(session);
-out: + return ret; + +err_ref_msg: + nlmsg_free(msg); +err_ref: + l2tp_session_dec_refcount(session); +err: return ret; }