net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces"

This reverts commits 6d04fe15f7 and
a31edb2059.

It turns out the idea to share a single pointer for both kernel and user
space address causes various kinds of problems.  So use the slightly less
optimal version that uses an extra bit, but which is guaranteed to be safe
everywhere.

Fixes: 6d04fe15f7 ("net: optimize the sockptr_t for unified kernel/user address spaces")
Reported-by: Eric Dumazet <edumazet@google.com>
Reported-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/bpfilter/sockopt.c

@@ -57,18 +57,16 @@ int bpfilter_ip_set_sockopt(struct sock *sk, int optname, sockptr_t optval,
 	return bpfilter_mbox_request(sk, optname, optval, optlen, true);
 }
 
-int bpfilter_ip_get_sockopt(struct sock *sk, int optname,
-			    char __user *user_optval, int __user *optlen)
+int bpfilter_ip_get_sockopt(struct sock *sk, int optname, char __user *optval,
+			    int __user *optlen)
 {
-	sockptr_t optval;
-	int err, len;
+	int len;
 
 	if (get_user(len, optlen))
 		return -EFAULT;
-	err = init_user_sockptr(&optval, user_optval, len);
-	if (err)
-		return err;
-	return bpfilter_mbox_request(sk, optname, optval, len, false);
+
+	return bpfilter_mbox_request(sk, optname, USER_SOCKPTR(optval), len,
+				     false);
 }
 
 static int __init bpfilter_sockopt_init(void)