[NETLINK]: negative groups in netlink_setsockopt

Reading netlink_setsockopt it's not immediately clear why there isn't a
bug when you pass in negative numbers, the reason being that the >=
comparison is really unsigned although 'val' is signed because
nlk->ngroups is unsigned. Make 'val' unsigned too.

[ Update the get_user() cast to match.  --DaveM ]
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/netlink/af_netlink.c

@@ -1012,13 +1012,14 @@ static int netlink_setsockopt(struct socket *sock, int level, int optname,
 {
 	struct sock *sk = sock->sk;
 	struct netlink_sock *nlk = nlk_sk(sk);
-	int val = 0, err;
+	unsigned int val = 0;
+	int err;
 
 	if (level != SOL_NETLINK)
 		return -ENOPROTOOPT;
 
 	if (optlen >= sizeof(int) &&
-	    get_user(val, (int __user *)optval))
+	    get_user(val, (unsigned int __user *)optval))
 		return -EFAULT;
 
 	switch (optname) {