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

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

[Christoph Hellwig]

The __user doesn't make sense when casting to an integer type.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 net/bpfilter/bpfilter_kern.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 977e9dad72ca4f..713b4b3d02005d 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -49,7 +49,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
 	req.is_set = is_set;
 	req.pid = current->pid;
 	req.cmd = optname;
-	req.addr = (long __force __user)optval;
+	req.addr = (__force long)optval;
 	req.len = optlen;
 	if (!bpfilter_ops.info.tgid)
 		goto out;
-- 
2.27.0

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

[Luc Van Oostenryck]

On Mon, Jul 20, 2020 at 02:47:15PM +0200, Christoph Hellwig wrote:
> The __user doesn't make sense when casting to an integer type.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> ---
>  net/bpfilter/bpfilter_kern.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
> index 977e9dad72ca4f..713b4b3d02005d 100644
> --- a/net/bpfilter/bpfilter_kern.c
> +++ b/net/bpfilter/bpfilter_kern.c
> @@ -49,7 +49,7 @@ static int __bpfilter_process_sockopt(struct sock *sk, int optname,
>  	req.is_set = is_set;
>  	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).

-- Luc

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

[Christoph Hellwig]

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

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

[Al Viro]

On Tue, Jul 21, 2020 at 07:23:26AM +0200, Christoph Hellwig wrote:
> 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

Cast to unsigned long.  Or to uintptr_t if you want to be fancy.