[NET]: Make sure l_linger is unsigned to avoid negative timeouts

One of my x86_64 (linux 2.6.13) server log is filled with :

schedule_timeout: wrong timeout value ffffffffffffff06 from ffffffff802e63ca
schedule_timeout: wrong timeout value ffffffffffffff06 from ffffffff802e63ca
schedule_timeout: wrong timeout value ffffffffffffff06 from ffffffff802e63ca
schedule_timeout: wrong timeout value ffffffffffffff06 from ffffffff802e63ca
schedule_timeout: wrong timeout value ffffffffffffff06 from ffffffff802e63ca

This is because some application does a

struct linger li;
li.l_onoff = 1;
li.l_linger = -1;
setsockopt(sock, SOL_SOCKET, SO_LINGER, &li, sizeof(li));

And unfortunatly l_linger is defined as a 'signed int' in
include/linux/socket.h:

struct linger {
         int             l_onoff;        /* Linger active                */
         int             l_linger;       /* How long to linger for       */
};

I dont know if it's safe to change l_linger to 'unsigned int' in the
include file (It might be defined as int in ABI specs)
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/sock.c

@@ -341,11 +341,11 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 				sock_reset_flag(sk, SOCK_LINGER);
 			else {
 #if (BITS_PER_LONG == 32)
-				if (ling.l_linger >= MAX_SCHEDULE_TIMEOUT/HZ)
+				if ((unsigned int)ling.l_linger >= MAX_SCHEDULE_TIMEOUT/HZ)
 					sk->sk_lingertime = MAX_SCHEDULE_TIMEOUT;
 				else
 #endif
-					sk->sk_lingertime = ling.l_linger * HZ;
+					sk->sk_lingertime = (unsigned int)ling.l_linger * HZ;
 				sock_set_flag(sk, SOCK_LINGER);
 			}
 			break;