Subject: Re: [patch] isdn/kcapi: return -EFAULT on copy_from_user errors

From: Jan Kiszka <[email-masked]>
Date: Thu, 03 Jun 2010 12:26:42 +0200

Dan Carpenter wrote:
> copy_from_user() returns the number of bytes remaining but we should
> return -EFAULT here.  The error code gets returned to the user.  Both 
> old_capi_manufacturer() and capi20_manufacturer() had other places
> that already returned -EFAULT so this won't break anything.
> 

Good point.

> Signed-off-by: Dan Carpenter <[email-masked]>
> 
> diff --git a/drivers/isdn/capi/kcapi.c b/drivers/isdn/capi/kcapi.c
> index bde3c88..b054494 100644
> --- a/drivers/isdn/capi/kcapi.c
> +++ b/drivers/isdn/capi/kcapi.c
> @@ -1020,12 +1020,12 @@ static int old_capi_manufacturer(unsigned int cmd, void __user *data)
>  		if (cmd == AVMB1_ADDCARD) {
>  		   if ((retval = copy_from_user(&cdef, data,
>  					    sizeof(avmb1_carddef))))
> -			   return retval;
> +			   return -EFAULT;
>  		   cdef.cardtype = AVM_CARDTYPE_B1;
>  		} else {
>  		   if ((retval = copy_from_user(&cdef, data,
>  					    sizeof(avmb1_extcarddef))))
> -			   return retval;
> +			   return -EFAULT;
>  		}
>  		cparams.port = cdef.port;
>  		cparams.irq = cdef.irq;
> @@ -1218,7 +1218,7 @@ int capi20_manufacturer(unsigned int cmd, void __user *data)
>  		kcapi_carddef cdef;
>  
>  		if ((retval = copy_from_user(&cdef, data, sizeof(cdef))))
> -			return retval;
> +			return -EFAULT;
>  
>  		cparams.port = cdef.port;
>  		cparams.irq = cdef.irq;

No need to assign retval anymore, it is overwritten in all non-error cases.

Jan