linux-kernel - Re: [PATCH] drivers/comedi: copy userspace array safely

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Date:   Fri, 03 Nov 2023 10:11:06 +0100
From:   Philipp Stanner <pstanner@...hat.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Ian Abbott <abbotti@....co.uk>,
        H Hartley Sweeten <hsweeten@...ionengravers.com>,
        Ivan Orlov <ivan.orlov0322@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        linux-kernel@...r.kernel.org, Dave Airlie <airlied@...hat.com>
Subject: Re: [PATCH] drivers/comedi: copy userspace array safely

On Fri, 2023-11-03 at 06:53 +0100, Greg Kroah-Hartman wrote:
> On Thu, Nov 02, 2023 at 08:08:49PM +0100, Philipp Stanner wrote:
> > comedi_fops.c utilizes memdup_user() to copy a userspace array. This
> > does not check for an overflow.
> 
> Is there potential for an overflow today?

None that I'm aware of, no. This is more about establishing the new
function as the standard for array-copying, thereby improving
readability and maybe robustness in case of future changes.

> 
> > 
> > Use the new wrapper memdup_array_user() to copy the array more safely.
> 
> How about saying something like:
>         "Use the new function memdup_array_user() in case things change
>         in the future which would prevent overflows if something were to
>         change in the size of the structures".
> 
> Or something to the affect of "all is good today, but make it easy to be
> correct in the future as well".

Yes, good idea. I'll send a better wording

P.

> 
> thanks,
> 
> greg k-h
>