linux-kernel - Re: [PATCH] misc: rtsx: improve status check

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Date:   Wed, 26 Aug 2020 16:40:06 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     trix@...hat.com
Cc:     arnd@...db.de, rikard.falkeborn@...il.com, rogerable@...ltek.com,
        lee.jones@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] misc: rtsx: improve status check

On Wed, Aug 26, 2020 at 06:53:37AM -0700, trix@...hat.com wrote:
> From: Tom Rix <trix@...hat.com>
> 
> clang static analysis flags this error
> 
> rtsx_usb.c:505:10: warning: The left operand of '&'
>   is a garbage value
>         if (val & cd_mask[card])
>             ~~~ ^
> 
> val is set when rtsx_usb_get_card_status() is successful.  The
> problem is how it checks its callers returns.
> 
> 	/* usb_control_msg may return positive when success */
> 	if (ret < 0)
> 		return ret;
> 
> This is correct for the usb_control_msg() the call. However,
> the call to rtsx_usb_get_status_with_bulk is only successful
> when 0 is returned.
> 
> So make status checking block specific.
> 
> Fixes: 730876be2566 ("mfd: Add realtek USB card reader driver")
> Signed-off-by: Tom Rix <trix@...hat.com>
> ---
>  drivers/misc/cardreader/rtsx_usb.c | 11 ++++++-----
>  1 file changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/misc/cardreader/rtsx_usb.c b/drivers/misc/cardreader/rtsx_usb.c
> index 59eda55d92a3..bd392b0c66af 100644
> --- a/drivers/misc/cardreader/rtsx_usb.c
> +++ b/drivers/misc/cardreader/rtsx_usb.c
> @@ -304,14 +304,15 @@ int rtsx_usb_get_card_status(struct rtsx_ucr *ucr, u16 *status)
>  		*status = *buf;
>  
>  		kfree(buf);
> +
> +		/* usb_control_msg may return positive when success */

it _WILL_ return positive.  it will return negative for an error.  It
will never return 0.

> +		if (ret < 0)
> +			return ret;
>  	} else {
>  		ret = rtsx_usb_get_status_with_bulk(ucr, status);
> +		if (ret)
> +			return ret;
>  	}
> -
> -	/* usb_control_msg may return positive when success */
> -	if (ret < 0)
> -		return ret;
> -

I fail to see how this code is incorrect today.

Well, I do see a bug in here, but you aren't fixing it (short read is
not checked), see the recent linux-usb@...r mail thread about that
problem that we will be fixing tree-wide over time soon...

How can your move of these lines modify anything?

thanks,

greg k-h