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 8e5a8b3b22c636e9935be288504dbf26f3b8eaf7..848072793fa98e7507a60bae3921f98d059d111e 100644 (file)
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2779,11 +2779,11 @@ 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);