linux-kernel - Re: [PATCH] USB: serial: fix invalid user-pointer checks

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Message-ID: <20161108154117.GN2664@localhost>
Date:   Tue, 8 Nov 2016 16:41:17 +0100
From:   Johan Hovold <johan@...nel.org>
To:     Oliver Neukum <oneukum@...e.com>
Cc:     Johan Hovold <johan@...nel.org>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] USB: serial: fix invalid user-pointer checks

On Tue, Nov 08, 2016 at 03:13:13PM +0100, Oliver Neukum wrote:
> On Tue, 2016-11-08 at 13:26 +0100, Johan Hovold wrote:
> > Drop invalid user-pointer checks from ioctl handlers.
> > 
> > A NULL-pointer can be valid in user space and copy_to_user() takes
> > care
> > of sanity checking.
> 
> Shouldn't we bail out early in these cases?

I don't think it's worth it, and this is also the general pattern for
such ioctls. The added overhead for an error case like this is really
negligible.

Thanks,
Johan