[PATCH 5.15 150/317] udp: fix incorrect parameter validation in the udp_lib_getsockopt() function

[Sasha Levin]

From: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>

[ Upstream commit 4bb3ba7b74fceec6f558745b25a43c6521cf5506 ]

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@xxxxxxxxxx>
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@xxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 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 c454daa78a2f8..2caf54c241037 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2814,11 +2814,11 @@ 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 = READ_ONCE(up->corkflag);
-- 
2.43.0