linux-kernel - Re: [PATCH] staging: comedi: comedi_fops.c: changed type in assignment to unsigned int *

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Date:   Wed, 15 Jul 2020 12:19:50 +0100
From:   Ian Abbott <abbotti@....co.uk>
To:     B K Karthik <bkkarthik@...u.pes.edu>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Xiyu Yang <xiyuyang19@...an.edu.cn>,
        Michel Lespinasse <walken@...gle.com>,
        Divyansh Kamboj <kambojdivyansh2000@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: comedi: comedi_fops.c: changed type in
 assignment to unsigned int *

On 15/07/2020 05:48, B K Karthik wrote:
> fixed a sparse warning by changing the type in
> assignment from void [noderef] __user * to unsigned int *
> (different address space)
> 
> Signed-off-by: B K Karthik <karthik.bk2000@...e.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 3f70e5dfac39..4cc012e231b7 100644
> --- a/drivers/staging/comedi/comedi_fops.c
> +++ b/drivers/staging/comedi/comedi_fops.c
> @@ -2956,7 +2956,7 @@ 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 *) compat_ptr(v32.chanlist);

That should be:

	cmd->chanlist = (unsigned int __force *)compat_ptr(v32.chanlist);

>   	cmd->chanlist_len = v32.chanlist_len;
>   	cmd->data = compat_ptr(v32.data);
>   	cmd->data_len = v32.data_len;
> 

A reverse cast is required in put_compat_cmd():

	v32.chanlist = ptr_to_compat((unsigned int __user *)cmd->chanlist);

Those changes will get rid of the sparse warnings.

-- 
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