3.2.95-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Guillaume Nault <g.nault@xxxxxxxxxxxx>
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.
Fixes: 309795f4bec2 ("l2tp: Add netlink control API for L2TP")
Signed-off-by: Guillaume Nault <g.nault@xxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: l2tp_tunnel_free() does more than just kfree_rcu(), so
don't remove it]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -112,7 +112,6 @@ struct l2tp_net {
};
static void l2tp_session_set_header_len(struct l2tp_session *session, int version);
-static void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel);
static inline struct l2tp_net *l2tp_pernet(const struct net *net)
@@ -123,33 +122,6 @@ static inline struct l2tp_net *l2tp_pern
}
-/* 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 { \
- printk(KERN_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 { \
- printk(KERN_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
@@ -225,6 +197,27 @@ struct l2tp_session *l2tp_session_find(s
}
EXPORT_SYMBOL_GPL(l2tp_session_find);
+/* 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);
+
/* Like l2tp_session_find() but takes a reference on the returned session.
* Optionally calls session->ref() too if do_ref is true.
*/
@@ -1341,7 +1334,7 @@ again:
/* 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)
+void l2tp_tunnel_free(struct l2tp_tunnel *tunnel)
{
struct l2tp_net *pn = l2tp_pernet(tunnel->l2tp_net);
@@ -1359,6 +1352,7 @@ static void l2tp_tunnel_free(struct l2tp
atomic_dec(&l2tp_tunnel_count);
}
+EXPORT_SYMBOL_GPL(l2tp_tunnel_free);
/* Create a socket for the tunnel, if one isn't set up by
* userspace. This is used for static tunnels where there is no
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -222,6 +222,9 @@ out:
return tunnel;
}
+struct l2tp_tunnel *l2tp_tunnel_get(const struct net *net, u32 tunnel_id);
+void l2tp_tunnel_free(struct l2tp_tunnel *tunnel);
+
struct l2tp_session *l2tp_session_get(const struct net *net,
struct l2tp_tunnel *tunnel,
u32 session_id, bool do_ref);
@@ -248,6 +251,17 @@ extern int l2tp_nl_register_ops(enum l2t
extern 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))
+ l2tp_tunnel_free(tunnel);
+}
+
/* Session reference counts. Incremented when code obtains a reference
* to a session.
*/
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -57,10 +57,12 @@ static struct l2tp_session *l2tp_nl_sess
(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;