net: Make setsockopt() optlen be unsigned.

This provides safety against negative optlen at the type
level instead of depending upon (sometimes non-trivial)
checks against this sprinkled all over the the place, in
each and every implementation.

Based upon work done by Arjan van de Ven and feedback
from Linus Torvalds.

Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index ebaaa7f..3326aff 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1359,7 +1359,7 @@
  *	Socket option code for UDP
  */
 int udp_lib_setsockopt(struct sock *sk, int level, int optname,
-		       char __user *optval, int optlen,
+		       char __user *optval, unsigned int optlen,
 		       int (*push_pending_frames)(struct sock *))
 {
 	struct udp_sock *up = udp_sk(sk);
@@ -1441,7 +1441,7 @@
 EXPORT_SYMBOL(udp_lib_setsockopt);
 
 int udp_setsockopt(struct sock *sk, int level, int optname,
-		   char __user *optval, int optlen)
+		   char __user *optval, unsigned int optlen)
 {
 	if (level == SOL_UDP  ||  level == SOL_UDPLITE)
 		return udp_lib_setsockopt(sk, level, optname, optval, optlen,
@@ -1451,7 +1451,7 @@
 
 #ifdef CONFIG_COMPAT
 int compat_udp_setsockopt(struct sock *sk, int level, int optname,
-			  char __user *optval, int optlen)
+			  char __user *optval, unsigned int optlen)
 {
 	if (level == SOL_UDP  ||  level == SOL_UDPLITE)
 		return udp_lib_setsockopt(sk, level, optname, optval, optlen,