linux-kernel - [PATCH net-next] l2tp: fix incorrect parameter validation in the pppol2tp

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Message-ID: <20240306095449.1782369-1-Ilia.Gavrilov@infotecs.ru>
Date: Wed, 6 Mar 2024 09:58:10 +0000
From: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
To: James Chapman <jchapman@...alix.com>
CC: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"lvc-project@...uxtesting.org" <lvc-project@...uxtesting.org>
Subject: [PATCH net-next] l2tp: fix incorrect parameter validation in the
 pppol2tp_getsockopt() function

The 'len' variable can't be negative because all 'min_t' parameters
cast to unsigned int, and then the minimum one is chosen.

To fix it, move the if statement higher.

Fixes: 3557baabf280 ("[L2TP]: PPP over L2TP driver core")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
---
 net/l2tp/l2tp_ppp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index f011af6601c9..6146e4e67bbb 100644
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -1356,11 +1356,11 @@ static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
 	if (get_user(len, optlen))
 		return -EFAULT;
 
-	len = min_t(unsigned int, len, sizeof(int));
-
 	if (len < 0)
 		return -EINVAL;
 
+	len = min_t(unsigned int, len, sizeof(int));
+
 	err = -ENOTCONN;
 	if (!sk->sk_user_data)
 		goto end;
-- 
2.39.2