pppoe: check sockaddr length in pppoe_connect()

[ Upstream commit a49e2f5d5fb141884452ddb428f551b123d436b5 ]

We must validate sockaddr_len, otherwise userspace can pass fewer data
than we expect and we end up accessing invalid data.

Fixes: 224cf5ad14c0 ("ppp: Move the PPP drivers")
Reported-by: syzbot+4f03bdf92fdf9ef5ddab@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>

diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index dc36c2ec1d1039c89011a6a8d5b7d862fafd5e6b..fa2c7bd638be945121f1ceba16c35be2b7bd70d9 100644 (file)
--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -620,6 +620,10 @@ static int pppoe_connect(struct socket *sock, struct sockaddr *uservaddr,
        lock_sock(sk);
 
        error = -EINVAL;
+
+       if (sockaddr_len != sizeof(struct sockaddr_pppox))
+               goto end;
+
        if (sp->sa_protocol != PX_PROTO_OE)
                goto end;