tcp: fix incorrect parameter validation in the do_tcp_getsockopt() function

[ Upstream commit 716edc9706deb3bb2ff56e2eeb83559cea8f22db ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index c82dc42f57c65df112f79080ff407cd98d11ce68..a4f41859231448b00378fb82219c8a47c33b41f3 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4010,11 +4010,11 @@ 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;