linux-kernel - Re: [PATCH] staging: wlan-ng: silence incorrect type in argument 1 (different address spaces) warning

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Date:   Sat, 24 Apr 2021 13:45:29 +0530
From:   Ashish Kalra <eashishkalra@...il.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ashish Kalra <eashishkalra@...il.com>,
        Abheek Dhawan <adawesomeguy222@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Romain Perier <romain.perier@...il.com>,
        Waiman Long <longman@...hat.com>,
        Allen Pais <apais@...ux.microsoft.com>,
        Ivan Safonov <insafonov@...il.com>,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: wlan-ng: silence incorrect type in argument 1
 (different address spaces) warning

On Fri, Apr 23, 2021 at 11:11:05PM -0700, Joe Perches wrote:
> On Sat, 2021-04-24 at 08:00 +0200, Greg Kroah-Hartman wrote:
> > On Fri, Apr 23, 2021 at 08:56:19PM +0530, Ashish Kalra wrote:
> > > On Thu, Apr 22, 2021 at 10:43:13AM +0200, Greg Kroah-Hartman wrote:
> > > > On Tue, Apr 20, 2021 at 02:31:42PM +0530, Ashish Kalra wrote:
> > > > > Upon running sparse, "warning: incorrect type in argument 1 (different address spaces)
> > > > > is brought to notice for this file.let's add correct typecast to make it cleaner and
> > > > > silence the Sparse warning.
> []
> > >  struct p80211ioctl_req {
> > >         char name[WLAN_DEVNAMELEN_MAX];
> > > -       caddr_t data;
> > > +       void __user *data;
> > > 
> > > Does this looks ok to you and is there any other check possible if this is ok?
> > 
> > Wait, what is "caddr_t"?  Try unwinding that mess first...
> 
> Might not be that simple.
> 
> include/linux/types.h:typedef __kernel_caddr_t  caddr_t;
> include/uapi/linux/coda.h:typedef void * caddr_t;
> include/uapi/asm-generic/posix_types.h:typedef char *           __kernel_caddr_t;
> 
> 
data is part of p80211ioctl_req and is used at two places only inside p80211knetdev_do_ioctl
it seems both places it will be used as void __user* only

	msgbuf = memdup_user(req->data, req->len);
        
	if (result == 0) {
                if (copy_to_user
                    ((void __user *)req->data, msgbuf, req->len)) {
                        result = -EFAULT;
                }
        }

Will it still be problem if we change it from char * to void *.?
is there any way to check how caller of this function will be using it?