udp: fix incorrect parameter validation in the udp_lib_getsockopt() function

[ 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@google.com>
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 476f79f1563a8aa993ff635f09a7bf338f324a2d..b2541c7d7c87f7cf02695581016e36ada368c8fd 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2748,11 +2748,11 @@ 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);