linux-kernel - Re: [PATCH] staging: comedi: cast to (unsigned int *)

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Date:   Wed, 17 Feb 2021 18:35:15 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Atul Gopinathan <atulgopinathan@...il.com>
Cc:     devel@...verdev.osuosl.org, abbotti@....co.uk,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: comedi: cast to (unsigned int *)

On Wed, Feb 17, 2021 at 10:29:08PM +0530, Atul Gopinathan wrote:
> Resolve the following warning generated by sparse:
> 
> drivers/staging//comedi/comedi_fops.c:2956:23: warning: incorrect type in assignment (different address spaces)
> drivers/staging//comedi/comedi_fops.c:2956:23:    expected unsigned int *chanlist
> drivers/staging//comedi/comedi_fops.c:2956:23:    got void [noderef] <asn:1> *
> 
> compat_ptr() has a return type of "void __user *"
> as defined in "include/linux/compat.h"
> 
> cmd->chanlist is of type "unsigned int *" as defined
> in drivers/staging/comedi/comedi.h" in struct
> comedi_cmd.
> 
> Signed-off-by: Atul Gopinathan <atulgopinathan@...il.com>
> ---
>  drivers/staging/comedi/comedi_fops.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
> index e85a99b68f31..fc4ec38012b4 100644
> --- a/drivers/staging/comedi/comedi_fops.c
> +++ b/drivers/staging/comedi/comedi_fops.c
> @@ -2953,7 +2953,7 @@ static int get_compat_cmd(struct comedi_cmd *cmd,
>  	cmd->scan_end_arg = v32.scan_end_arg;
>  	cmd->stop_src = v32.stop_src;
>  	cmd->stop_arg = v32.stop_arg;
> -	cmd->chanlist = compat_ptr(v32.chanlist);
> +	cmd->chanlist = (unsigned int __force *)compat_ptr(v32.chanlist);

__force?  That feels wrong, something is odd if that is ever needed.

Are you _sure_ this is correct?

greg k-h