[IPv6]: Fix incorrect length check in rawv6_sendmsg()

In article <20070329.142644.70222545.davem@davemloft.net> (at Thu, 29 Mar 2007 14:26:44 -0700 (PDT)), David Miller <davem@davemloft.net> says:

> From: Sridhar Samudrala <sri@us.ibm.com>
> Date: Thu, 29 Mar 2007 14:17:28 -0700
>
> > The check for length in rawv6_sendmsg() is incorrect.
> > As len is an unsigned int, (len < 0) will never be TRUE.
> > I think checking for IPV6_MAXPLEN(65535) is better.
> >
> > Is it possible to send ipv6 jumbo packets using raw
> > sockets? If so, we can remove this check.
>
> I don't see why such a limitation against jumbo would exist,
> does anyone else?
>
> Thanks for catching this Sridhar.  A good compiler should simply
> fail to compile "if (x < 0)" when 'x' is an unsigned type, don't
> you think :-)

Dave, we use "int" for returning value,
so we should fix this anyway, IMHO;
we should not allow len > INT_MAX.
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Acked-by: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv6/raw.c

@@ -687,9 +687,9 @@ static int rawv6_sendmsg(struct kiocb *iocb, struct sock *sk,
 	int err;
 
 	/* Rough check on arithmetic overflow,
-	   better check is made in ip6_build_xmit
+	   better check is made in ip6_append_data().
 	 */
-	if (len < 0)
+	if (len > INT_MAX)
 		return -EMSGSIZE;
 
 	/* Mirror BSD error message compatibility */

net/ipv6/udp.c

@@ -615,7 +615,7 @@ do_udp_sendmsg:
 		return udp_sendmsg(iocb, sk, msg, len);
 
 	/* Rough check on arithmetic overflow,
-	   better check is made in ip6_build_xmit
+	   better check is made in ip6_append_data().
 	   */
 	if (len > INT_MAX - sizeof(struct udphdr))
 		return -EMSGSIZE;