4 files changed, 30 insertions, 0 deletions
diff --git a/net/l2tp/l2tp_core.c b/net/l2tp/l2tp_core.c
index 26f1d435696a..dd5ba0c11ab3 100644
--- a/net/l2tp/l2tp_core.c
+++ b/net/l2tp/l2tp_core.c
@@ -884,6 +884,10 @@ static int l2tp_udp_recv_core(struct l2tp_tunnel *tunnel, struct sk_buff *skb)
 		goto error;
 	}
 
+	if (tunnel->version == L2TP_HDR_VER_3 &&
+	    l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+		goto error;
+
 	l2tp_recv_common(session, skb, ptr, optr, hdrflags, length);
 	l2tp_session_dec_refcount(session);
 
diff --git a/net/l2tp/l2tp_core.h b/net/l2tp/l2tp_core.h
index 9c9afe94d389..b2ce90260c35 100644
--- a/net/l2tp/l2tp_core.h
+++ b/net/l2tp/l2tp_core.h
@@ -301,6 +301,26 @@ static inline bool l2tp_tunnel_uses_xfrm(const struct l2tp_tunnel *tunnel)
 }
 #endif
 
+static inline int l2tp_v3_ensure_opt_in_linear(struct l2tp_session *session, struct sk_buff *skb,
+					       unsigned char **ptr, unsigned char **optr)
+{
+	int opt_len = session->peer_cookie_len + l2tp_get_l2specific_len(session);
+
+	if (opt_len > 0) {
+		int off = *ptr - *optr;
+
+		if (!pskb_may_pull(skb, off + opt_len))
+			return -1;
+
+		if (skb->data != *optr) {
+			*optr = skb->data;
+			*ptr = skb->data + off;
+		}
+	}
+
+	return 0;
+}
+
 #define l2tp_printk(ptr, type, func, fmt, ...)				\
 do {									\
 	if (((ptr)->debug) & (type))					\
diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 35f6f86d4dcc..d4c60523c549 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -165,6 +165,9 @@ static int l2tp_ip_recv(struct sk_buff *skb)
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
 	}
 
+	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+		goto discard_sess;
+
 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
 	l2tp_session_dec_refcount(session);
 
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 237f1a4a0b0c..0ae6899edac0 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -178,6 +178,9 @@ static int l2tp_ip6_recv(struct sk_buff *skb)
 		print_hex_dump_bytes("", DUMP_PREFIX_OFFSET, ptr, length);
 	}
 
+	if (l2tp_v3_ensure_opt_in_linear(session, skb, &ptr, &optr))
+		goto discard_sess;
+
 	l2tp_recv_common(session, skb, ptr, optr, 0, skb->len);
 	l2tp_session_dec_refcount(session);