tcp: fix incorrect parameter validation in the do_tcp_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")
Signed-off-by: Gavrilov Ilia <Ilia.Gavrilov@infotecs.ru>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c5b83875411aee6037d0afd060eb9d3e16f8b6b0..b091149742b1d0103e25981e940c17fae1b4d917 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4011,11 +4011,11 @@ int do_tcp_getsockopt(struct sock *sk, int level,
        if (copy_from_sockptr(&len, optlen, sizeof(int)))
                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 TCP_MAXSEG:
                val = tp->mss_cache;