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Date: Mon, 12 Feb 2018 10:11:11 +0000
From: James Chapman <jchapman@...alix.com>
To: netdev@...r.kernel.org
Cc: kbuild-all@...org
Subject: [PATCH net-next v2 07/16] l2tp: hide sessions if they are closing
Replace the dead flag in the session context with a closing flag and
spinlock. Check it in session lookup functions such that we don't try
to access session data while it is being destroyed.
---
net/l2tp/l2tp_core.c | 34 +++++++++++++++++++++++++++++++++-
net/l2tp/l2tp_core.h | 2 ++
2 files changed, 35 insertions(+), 1 deletion(-)
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 477b96cf8ab3..869dec89ff0f 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -198,7 +198,14 @@ struct l2tp_session *l2tp_session_get(const struct net *net,
rcu_read_lock_bh();
hlist_for_each_entry_rcu(session, session_list, global_hlist) {
if (session->session_id == session_id) {
+ spin_lock_bh(&session->lock);
+ if (session->closing) {
+ spin_unlock_bh(&session->lock);
+ rcu_read_unlock_bh();
+ return NULL;
+ }
l2tp_session_inc_refcount(session);
+ spin_unlock_bh(&session->lock);
rcu_read_unlock_bh();
return session;
@@ -213,7 +220,14 @@ struct l2tp_session *l2tp_session_get(const struct net *net,
read_lock_bh(&tunnel->hlist_lock);
hlist_for_each_entry(session, session_list, hlist) {
if (session->session_id == session_id) {
+ spin_lock_bh(&session->lock);
+ if (session->closing) {
+ spin_unlock_bh(&session->lock);
+ read_unlock_bh(&tunnel->hlist_lock);
+ return NULL;
+ }
l2tp_session_inc_refcount(session);
+ spin_unlock_bh(&session->lock);
read_unlock_bh(&tunnel->hlist_lock);
return session;
@@ -234,6 +248,12 @@ struct l2tp_session *l2tp_session_get_nth(struct l2tp_tunnel *tunnel, int nth)
read_lock_bh(&tunnel->hlist_lock);
for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
hlist_for_each_entry(session, &tunnel->session_hlist[hash], hlist) {
+ spin_lock_bh(&session->lock);
+ if (session->closing) {
+ spin_unlock_bh(&session->lock);
+ continue;
+ }
+ spin_unlock_bh(&session->lock);
if (++count > nth) {
l2tp_session_inc_refcount(session);
read_unlock_bh(&tunnel->hlist_lock);
@@ -261,6 +281,12 @@ struct l2tp_session *l2tp_session_get_by_ifname(const struct net *net,
rcu_read_lock_bh();
for (hash = 0; hash < L2TP_HASH_SIZE_2; hash++) {
hlist_for_each_entry_rcu(session, &pn->l2tp_session_hlist[hash], global_hlist) {
+ spin_lock_bh(&session->lock);
+ if (session->closing) {
+ spin_unlock_bh(&session->lock);
+ continue;
+ }
+ spin_unlock_bh(&session->lock);
if (!strcmp(session->ifname, ifname)) {
l2tp_session_inc_refcount(session);
rcu_read_unlock_bh();
@@ -1678,8 +1704,13 @@ void __l2tp_session_unhash(struct l2tp_session *session)
*/
int l2tp_session_delete(struct l2tp_session *session)
{
- if (test_and_set_bit(0, &session->dead))
+ spin_lock_bh(&session->lock);
+ if (session->closing) {
+ spin_unlock_bh(&session->lock);
return 0;
+ }
+ session->closing = true;
+ spin_unlock_bh(&session->lock);
__l2tp_session_unhash(session);
l2tp_session_queue_purge(session);
@@ -1747,6 +1778,7 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
INIT_HLIST_NODE(&session->hlist);
INIT_HLIST_NODE(&session->global_hlist);
+ spin_lock_init(&session->lock);
/* Inherit debug options from tunnel */
session->debug = tunnel->debug;
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 4e098c822cd1..d28d91600ad5 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -75,6 +75,8 @@ struct l2tp_session {
int magic; /* should be
* L2TP_SESSION_MAGIC */
long dead;
+ bool closing;
+ spinlock_t lock; /* protect closing */
struct l2tp_tunnel *tunnel; /* back pointer to tunnel
* context */
--
1.9.1
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