[SCTP]: Add RCU synchronization around sctp_localaddr_list
sctp_localaddr_list is modified dynamically via NETDEV_UP
and NETDEV_DOWN events, but there is not synchronization
between writer (even handler) and readers. As a result,
the readers can access an entry that has been freed and
crash the sytem.
Signed-off-by: Vlad Yasevich <vladislav.yasevich@hp.com>
Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Sridhar Samdurala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index e98579b..7ee120e 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -153,6 +153,9 @@
addr->a.v4.sin_family = AF_INET;
addr->a.v4.sin_port = 0;
addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
+ addr->valid = 1;
+ INIT_LIST_HEAD(&addr->list);
+ INIT_RCU_HEAD(&addr->rcu);
list_add_tail(&addr->list, addrlist);
}
}
@@ -192,16 +195,24 @@
}
}
+void sctp_local_addr_free(struct rcu_head *head)
+{
+ struct sctp_sockaddr_entry *e = container_of(head,
+ struct sctp_sockaddr_entry, rcu);
+ kfree(e);
+}
+
/* Copy the local addresses which are valid for 'scope' into 'bp'. */
int sctp_copy_local_addr_list(struct sctp_bind_addr *bp, sctp_scope_t scope,
gfp_t gfp, int copy_flags)
{
struct sctp_sockaddr_entry *addr;
int error = 0;
- struct list_head *pos, *temp;
- list_for_each_safe(pos, temp, &sctp_local_addr_list) {
- addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+ rcu_read_lock();
+ list_for_each_entry_rcu(addr, &sctp_local_addr_list, list) {
+ if (!addr->valid)
+ continue;
if (sctp_in_scope(&addr->a, scope)) {
/* Now that the address is in scope, check to see if
* the address type is really supported by the local
@@ -221,6 +232,7 @@
}
end_copy:
+ rcu_read_unlock();
return error;
}
@@ -600,13 +612,18 @@
seq_printf(seq, "%d.%d.%d.%d ", NIPQUAD(addr->v4.sin_addr));
}
-/* Event handler for inet address addition/deletion events. */
+/* Event handler for inet address addition/deletion events.
+ * The sctp_local_addr_list needs to be protocted by a spin lock since
+ * multiple notifiers (say IPv4 and IPv6) may be running at the same
+ * time and thus corrupt the list.
+ * The reader side is protected with RCU.
+ */
static int sctp_inetaddr_event(struct notifier_block *this, unsigned long ev,
void *ptr)
{
struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
- struct sctp_sockaddr_entry *addr;
- struct list_head *pos, *temp;
+ struct sctp_sockaddr_entry *addr = NULL;
+ struct sctp_sockaddr_entry *temp;
switch (ev) {
case NETDEV_UP:
@@ -615,19 +632,25 @@
addr->a.v4.sin_family = AF_INET;
addr->a.v4.sin_port = 0;
addr->a.v4.sin_addr.s_addr = ifa->ifa_local;
- list_add_tail(&addr->list, &sctp_local_addr_list);
+ addr->valid = 1;
+ spin_lock_bh(&sctp_local_addr_lock);
+ list_add_tail_rcu(&addr->list, &sctp_local_addr_list);
+ spin_unlock_bh(&sctp_local_addr_lock);
}
break;
case NETDEV_DOWN:
- list_for_each_safe(pos, temp, &sctp_local_addr_list) {
- addr = list_entry(pos, struct sctp_sockaddr_entry, list);
+ spin_lock_bh(&sctp_local_addr_lock);
+ list_for_each_entry_safe(addr, temp,
+ &sctp_local_addr_list, list) {
if (addr->a.v4.sin_addr.s_addr == ifa->ifa_local) {
- list_del(pos);
- kfree(addr);
+ addr->valid = 0;
+ list_del_rcu(&addr->list);
break;
}
}
-
+ spin_unlock_bh(&sctp_local_addr_lock);
+ if (addr && !addr->valid)
+ call_rcu(&addr->rcu, sctp_local_addr_free);
break;
}
@@ -1160,6 +1183,7 @@
/* Initialize the local address list. */
INIT_LIST_HEAD(&sctp_local_addr_list);
+ spin_lock_init(&sctp_local_addr_lock);
sctp_get_local_addr_list();
/* Register notifier for inet address additions/deletions. */
@@ -1227,6 +1251,9 @@
sctp_v6_del_protocol();
inet_del_protocol(&sctp_protocol, IPPROTO_SCTP);
+ /* Unregister notifier for inet address additions/deletions. */
+ unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
+
/* Free the local address list. */
sctp_free_local_addr_list();
@@ -1240,9 +1267,6 @@
inet_unregister_protosw(&sctp_stream_protosw);
inet_unregister_protosw(&sctp_seqpacket_protosw);
- /* Unregister notifier for inet address additions/deletions. */
- unregister_inetaddr_notifier(&sctp_inetaddr_notifier);
-
sctp_sysctl_unregister();
list_del(&sctp_ipv4_specific.list);