From: Guillaume Nault g.nault@alphalink.fr
commit 54652eb12c1b72e9602d09cb2821d5760939190f upstream.
l2tp_tunnel_find() doesn't take a reference on the returned tunnel. Therefore, it's unsafe to use it because the returned tunnel can go away on us anytime.
Fix this by defining l2tp_tunnel_get(), which works like l2tp_tunnel_find(), but takes a reference on the returned tunnel. Caller then has to drop this reference using l2tp_tunnel_dec_refcount().
As l2tp_tunnel_dec_refcount() needs to be moved to l2tp_core.h, let's simplify the patch and not move the L2TP_REFCNT_DEBUG part. This code has been broken (not even compiling) in May 2012 by commit a4ca44fa578c ("net: l2tp: Standardize logging styles") and fixed more than two years later by commit 29abe2fda54f ("l2tp: fix missing line continuation"). So it doesn't appear to be used by anyone.
Same thing for l2tp_tunnel_free(); instead of moving it to l2tp_core.h, let's just simplify things and call kfree_rcu() directly in l2tp_tunnel_dec_refcount(). Extra assertions and debugging code provided by l2tp_tunnel_free() didn't help catching any of the reference counting and socket handling issues found while working on this series.
Backporting Notes
l2tp_core.c: This patch deletes some code / moves some code to l2tp_core.h and follows the patch (not including in this series) that switched from atomic to refcount_t. Moved code changed back to atomic.
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: Giuliano Procida gprocida@google.com --- net/l2tp/l2tp_core.c | 66 +++++++++++++---------------------------- net/l2tp/l2tp_core.h | 13 ++++++++ net/l2tp/l2tp_netlink.c | 6 ++-- 3 files changed, 38 insertions(+), 47 deletions(-)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c index c0abd5efd824..e5210cf8cb59 100644 --- a/net/l2tp/l2tp_core.c +++ b/net/l2tp/l2tp_core.c @@ -112,7 +112,6 @@ struct l2tp_net { spinlock_t l2tp_session_hlist_lock; };
-static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
static inline struct l2tp_tunnel *l2tp_tunnel(struct sock *sk) { @@ -126,39 +125,6 @@ static inline struct l2tp_net *l2tp_pernet(const struct net *net) return net_generic(net, l2tp_net_id); }
-/* Tunnel reference counts. Incremented per session that is added to - * the tunnel. - */ -static inline void l2tp_tunnel_inc_refcount_1(struct l2tp_tunnel *tunnel) -{ - atomic_inc(&tunnel->ref_count); -} - -static inline void l2tp_tunnel_dec_refcount_1(struct l2tp_tunnel *tunnel) -{ - if (atomic_dec_and_test(&tunnel->ref_count)) - l2tp_tunnel_free(tunnel); -} -#ifdef L2TP_REFCNT_DEBUG -#define l2tp_tunnel_inc_refcount(_t) \ -do { \ - pr_debug("l2tp_tunnel_inc_refcount: %s:%d %s: cnt=%d\n", \ - __func__, __LINE__, (_t)->name, \ - atomic_read(&_t->ref_count)); \ - l2tp_tunnel_inc_refcount_1(_t); \ -} while (0) -#define l2tp_tunnel_dec_refcount(_t) \ -do { \ - pr_debug("l2tp_tunnel_dec_refcount: %s:%d %s: cnt=%d\n", \ - __func__, __LINE__, (_t)->name, \ - atomic_read(&_t->ref_count)); \ - l2tp_tunnel_dec_refcount_1(_t); \ -} while (0) -#else -#define l2tp_tunnel_inc_refcount(t) l2tp_tunnel_inc_refcount_1(t) -#define l2tp_tunnel_dec_refcount(t) l2tp_tunnel_dec_refcount_1(t) -#endif - /* Session hash global list for L2TPv3. * The session_id SHOULD be random according to RFC3931, but several * L2TP implementations use incrementing session_ids. So we do a real @@ -228,6 +194,27 @@ l2tp_session_id_hash(struct l2tp_tunnel *tunnel, u32 session_id) return &tunnel->session_hlist[hash_32(session_id, L2TP_HASH_BITS)]; }
+/* Lookup a tunnel. A new reference is held on the returned tunnel. */ +struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id) +{ + const struct l2tp_net *pn = l2tp_pernet(net); + struct l2tp_tunnel *tunnel; + + rcu_read_lock_bh(); + list_for_each_entry_rcu(tunnel, &pn->l2tp_tunnel_list, list) { + if (tunnel->tunnel_id == tunnel_id) { + l2tp_tunnel_inc_refcount(tunnel); + rcu_read_unlock_bh(); + + return tunnel; + } + } + rcu_read_unlock_bh(); + + return NULL; +} +EXPORT_SYMBOL_GPL(l2tp_tunnel_get); + /* Lookup a session. A new reference is held on the returned session. * Optionally calls session->ref() too if do_ref is true. */ @@ -1351,17 +1338,6 @@ static void l2tp_udp_encap_destroy(struct sock *sk) } }
-/* Really kill the tunnel. - * Come here only when all sessions have been cleared from the tunnel. - */ -static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel) -{ - BUG_ON(atomic_read(&tunnel->ref_count) != 0); - BUG_ON(tunnel->sock != NULL); - l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: free...\n", tunnel->name); - kfree_rcu(tunnel, rcu); -} - /* Workqueue tunnel deletion function */ static void l2tp_tunnel_del_work(struct work_struct *work) { diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h index 8fa4ad103c25..0d4590b25592 100644 --- a/net/l2tp/l2tp_core.h +++ b/net/l2tp/l2tp_core.h @@ -234,6 +234,8 @@ out: return tunnel; }
+struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id); + struct l2tp_session *l2tp_session_get(const struct net *net, struct l2tp_tunnel *tunnel, u32 session_id, bool do_ref); @@ -272,6 +274,17 @@ int l2tp_nl_register_ops(enum l2tp_pwtype pw_type, void l2tp_nl_unregister_ops(enum l2tp_pwtype pw_type); int l2tp_ioctl(struct sock *sk, int cmd, unsigned long arg);
+static inline void l2tp_tunnel_inc_refcount(struct l2tp_tunnel *tunnel) +{ + atomic_inc(&tunnel->ref_count); +} + +static inline void l2tp_tunnel_dec_refcount(struct l2tp_tunnel *tunnel) +{ + if (atomic_dec_and_test(&tunnel->ref_count)) + kfree_rcu(tunnel, rcu); +} + /* Session reference counts. Incremented when code obtains a reference * to a session. */ diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c index afee3d54e5ef..558327d62167 100644 --- a/net/l2tp/l2tp_netlink.c +++ b/net/l2tp/l2tp_netlink.c @@ -72,10 +72,12 @@ static struct l2tp_session *l2tp_nl_session_get(struct genl_info *info, (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) + tunnel = l2tp_tunnel_get(net, tunnel_id); + if (tunnel) { session = l2tp_session_get(net, tunnel, session_id, do_ref); + l2tp_tunnel_dec_refcount(tunnel); + } }
return session;