Subject: Re: [PATCH 02/24] bpfilter: fix up a sparse annotation

From: Christoph Hellwig <[email-masked]>
Date: Tue, 21 Jul 2020 07:23:26 +0200

On Tue, Jul 21, 2020 at 04:40:16AM +0200, Luc Van Oostenryck wrote:
> >  	req.pid = current->pid;
> >  	req.cmd = optname;
> > -	req.addr = (long __force __user)optval;
> > +	req.addr = (__force long)optval;
> 
> For casts to integers, even '__force' is not needed (since integers
> can't be dereferenced, the concept of address-space is meaningless
> for them, so it's never useful to warn when it's dropped and
> '__force' is thus not needed).

That's what I thought. but if I remove it here I actually do get a
warning:

CHECK   net/bpfilter/bpfilter_kern.c
net/bpfilter/bpfilter_kern.c:52:21: warning: cast removes address space '__user' of expression

Using this recent sparse build:

hch@brick:~/work/linux$ sparse --version
v0.6.2-49-g707c5017