l2tp: fix race in l2tp_recv_common()
commit 61b9a047729bb230978178bca6729689d0c50ca2 upstream.
Taking a reference on sessions in l2tp_recv_common() is racy; this
has to be done by the callers.
To this end, a new function is required (l2tp_session_get()) to
atomically lookup a session and take a reference on it. Callers then
have to manually drop this reference.
Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index a4b0c92..b10abef 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -156,19 +156,19 @@
}
/* Ok, this is a data packet. Lookup the session. */
- session = l2tp_session_find(net, NULL, session_id);
- if (session == NULL)
+ session = l2tp_session_get(net, NULL, session_id, true);
+ if (!session)
goto discard;
tunnel = session->tunnel;
- if (tunnel == NULL)
- goto discard;
+ if (!tunnel)
+ goto discard_sess;
/* Trace packet contents, if enabled */
if (tunnel->debug & L2TP_MSG_DATA) {
length = min(32u, skb->len);
if (!pskb_may_pull(skb, length))
- goto discard;
+ goto discard_sess;
/* Point to L2TP header */
optr = ptr = skb->data;
@@ -179,6 +179,8 @@
l2tp_recv_common(session, skb, ptr, optr, 0, skb->len,
tunnel->recv_payload_hook);
+ l2tp_session_dec_refcount(session);
+
return 0;
pass_up:
@@ -216,6 +218,12 @@
return sk_receive_skb(sk, skb, 1);
+discard_sess:
+ if (session->deref)
+ session->deref(session);
+ l2tp_session_dec_refcount(session);
+ goto discard;
+
discard_put:
sock_put(sk);