linux-kernel - [PATCH net-next v2 2/6] udp: fix incorrect parameter validation in the udp_lib

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Date: Thu, 7 Mar 2024 14:23:50 +0000
From: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
CC: "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, "Paolo
 Abeni" <pabeni@...hat.com>, Simon Horman <horms@...nel.org>,
	"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>, "Willem de
 Bruijn" <willemb@...gle.com>
Subject: [PATCH net-next v2 2/6] udp: fix incorrect parameter validation in
 the udp_lib_getsockopt() function

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

To fix the logic, check 'len' as read from 'optlen',
where the types of relevant variables are (signed) int.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reviewed-by: Willem de Bruijn <willemb@...gle.com>
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@...otecs.ru>
---
V2:
 - reword the patch description
 net/ipv4/udp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index e474b201900f..17231c0f8830 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2792,11 +2792,11 @@ int udp_lib_getsockopt(struct sock *sk, 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));
+
 	switch (optname) {
 	case UDP_CORK:
 		val = udp_test_bit(CORK, sk);
-- 
2.39.2