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authorGuillaume Nault <g.nault@alphalink.fr>2017-08-25 16:51:40 +0200
committerDavid S. Miller <davem@davemloft.net>2017-08-28 11:34:58 -0700
commit54652eb12c1b72e9602d09cb2821d5760939190f (patch)
tree3f53546dd44567d09e5070f0dbc8917902f6882e /net/l2tp/l2tp_core.c
parent9ee369a405c57613d7c83a3967780c3e30c52ecc (diff)
l2tp: hold tunnel while looking up sessions in l2tp_netlink
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. 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>
Diffstat (limited to 'net/l2tp/l2tp_core.c')
-rw-r--r--net/l2tp/l2tp_core.c66
1 files changed, 21 insertions, 45 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index f363669eae47..90165a6874bc 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -113,7 +113,6 @@ 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)
{
@@ -127,39 +126,6 @@ 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)
-{
- refcount_inc(&tunnel->ref_count);
-}
-
-static inline void l2tp_tunnel_dec_refcount_1(struct l2tp_tunnel *tunnel)
-{
- if (refcount_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, \
- refcount_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, \
- refcount_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
@@ -229,6 +195,27 @@ 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.
*/
@@ -1348,17 +1335,6 @@ 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(refcount_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)
{