netdev - [PATCH net] pppoe: check sockaddr length in pppoe

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Message-ID: <387ca48810af36f2626049008a795d1adc375cb8.1524494257.git.g.nault@alphalink.fr>
Date:   Mon, 23 Apr 2018 16:38:27 +0200
From:   Guillaume Nault <g.nault@...halink.fr>
To:     netdev@...r.kernel.org
Cc:     Michal Ostrowski <mostrows@...thlink.net>
Subject: [PATCH net] pppoe: check sockaddr length in pppoe_connect()

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@...kaller.appspotmail.com
Signed-off-by: Guillaume Nault <g.nault@...halink.fr>
---
 drivers/net/ppp/pppoe.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
index 1483bc7b01e1..7df07337d69c 100644
--- 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;
 
-- 
2.17.0