Re: [PATCH] decnet: incorrect optlen size

[David Miller <davem@davemloft.net>]

From: steve@chygwyn.com
Date: Thu, 29 Jan 2009 08:58:58 +0000

> On Thu, Jan 29, 2009 at 09:21:15AM +0100, Roel Kluin wrote:
> > @@ -1359,10 +1359,10 @@ static int __dn_setsockopt(struct socket *sock, int level,int optname, char __us
> >  	if (optlen && !optval)
> >  		return -EINVAL;
> >  
> > -	if (optlen > sizeof(u))
> > +	if (optlen < sizeof(u))
> >  		return -EINVAL;
> >
> I don't see that this makes sense... we want to ensure that the passed
> length is less than the size of the union which we are going to use
> as a buffer.
>   
> > -	if (copy_from_user(&u, optval, optlen))
> > +	if (copy_from_user(&u, optval, sizeof(u)))
> >  		return -EFAULT;
> >
>  ... and here we only want to copy the amount of data that has actually
> been supplied, not the whole buffer size since in many cases the
> amount of data is less than the total buffer size.

This code is fine as-is, every single case statement below
this code makes an explicit optlen equality check before
deferencing any member of the union object we copy into.

I'm therefore dropping this patch.