[PATCH 4.4 30/50] l2tp: check sockaddr length in pppol2tp_connect()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Guillaume Nault <g.nault@alphalink.fr>


[ Upstream commit eb1c28c05894a4b1f6b56c5bf072205e64cfa280 ]

Check sockaddr_len before dereferencing sp->sa_protocol, to ensure that
it actually points to valid data.

Fixes: fd558d186df2 ("l2tp: Split pppol2tp patch into separate l2tp and ppp parts")
Reported-by: syzbot+a70ac890b23b1bf29f5c@syzkaller.appspotmail.com
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/l2tp/l2tp_ppp.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -606,6 +606,13 @@ static int pppol2tp_connect(struct socke
 	lock_sock(sk);
 
 	error = -EINVAL;
+
+	if (sockaddr_len != sizeof(struct sockaddr_pppol2tp) &&
+	    sockaddr_len != sizeof(struct sockaddr_pppol2tpv3) &&
+	    sockaddr_len != sizeof(struct sockaddr_pppol2tpin6) &&
+	    sockaddr_len != sizeof(struct sockaddr_pppol2tpv3in6))
+		goto end;
+
 	if (sp->sa_protocol != PX_PROTO_OL2TP)
 		goto end;