On Tue, Jul 21, 2020 at 04:40:16AM +0200, Luc Van Oostenryck wrote:

quoted

 	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