[PATCH 3.18 15/24] pppoe: check sockaddr length in pppoe_connect()

[Greg Kroah-Hartman]

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

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

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


[ 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+4f03bdf92fdf9ef5d...@syzkaller.appspotmail.com
Signed-off-by: Guillaume Nault <g.na...@alphalink.fr>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/net/ppp/pppoe.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/net/ppp/pppoe.c
+++ b/drivers/net/ppp/pppoe.c
@@ -613,6 +613,10 @@ static int pppoe_connect(struct socket *
        lock_sock(sk);
 
        error = -EINVAL;
+
+       if (sockaddr_len != sizeof(struct sockaddr_pppox))
+               goto end;
+
        if (sp->sa_protocol != PX_PROTO_OE)
                goto end;