[2/2] USB: usbdevfs: restore warning for nonsensical flags

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Sep 06, 2018 at 11:34:04AM -0400, Alan Stern wrote:
> On Thu, 6 Sep 2018, Oliver Neukum wrote:
> 
> > On Mi, 2018-09-05 at 15:07 +0200, Greg KH wrote:
> > > On Wed, Sep 05, 2018 at 03:02:48PM +0200, Oliver Neukum wrote:
> > > > On Mi, 2018-09-05 at 14:19 +0200, Greg KH wrote:
> > > > > On Wed, Sep 05, 2018 at 12:07:03PM +0200, Oliver Neukum wrote:
> > 
> > > > > > +	if (!allow_short && uurb->flags & USBDEVFS_URB_SHORT_NOT_OK)
> > > > > > +		dev_warn(&ps->dev->dev, "Requested nonsensical USBDEVFS_URB_SHORT_NOT_OK.\n");
> > > > > > +	if (!allow_zero && uurb->flags & USBDEVFS_URB_ZERO_PACKET)
> > > > > > +		dev_warn(&ps->dev->dev, "Requested nonsensical USBDEVFS_URB_ZERO_PACKET.\n");
> > > > > 
> > > > > We should not make it trivial for userspace to spam the kernel log if at
> > > > > all possible.  Returning an error is probably the better thing to do
> > > > > here, not just silently fix it up or ignore it.
> > > > 
> > > > That means a change in the API in a way that makes orking systems fail.
> > > 
> > > Ah, good point.
> > 
> > Well, but do we want to do this in the next major release even if we
> > cannot do it in a stable release?
> > 
> > >   I guess they were hitting the same dev_WARN() messages
> > > today anyway, right?
> > 
> > Yes. And for a kernel problem you really want the stack traces.
> > Still, that does not tell us that we want to print a message if
> > user space messes up. So dev_warn() or nothing?
> 
> An alternative is for usbfs to silently fix the flags when they are
> wrong.  Would that be any better?

Probably not.  I'll take the original patches now and see if there is
any complaints by users.

thanks,

greg k-h