ipmr: fix incorrect parameter validation in the ip_mroute_getsockopt() function

The 'olr' 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 'olr' 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>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 0708ac6f6c582681ab1f2b52c5ce1f2a4acd10de..fd5c01c8489f0f8a73c5f0a4178c0e761ddb3b7b 100644 (file)
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -1603,9 +1603,11 @@ int ip_mroute_getsockopt(struct sock *sk, int optname, sockptr_t optval,
 
        if (copy_from_sockptr(&olr, optlen, sizeof(int)))
                return -EFAULT;
-       olr = min_t(unsigned int, olr, sizeof(int));
        if (olr < 0)
                return -EINVAL;
+
+       olr = min_t(unsigned int, olr, sizeof(int));
+
        if (copy_to_sockptr(optlen, &olr, sizeof(int)))
                return -EFAULT;
        if (copy_to_sockptr(optval, &val, olr))