On Tue, 4 Sep 2018, Johan Hovold wrote:
> On Tue, Sep 04, 2018 at 12:21:09PM +0200, Oliver Neukum wrote:
> > On Di, 2018-09-04 at 11:31 +0200, Johan Hovold wrote:
> > > On Tue, Sep 04, 2018 at 10:44:41AM +0200, Oliver Neukum wrote:
> > > > For those people who run with panic_on_warn a WARN() triggered
> > > > from user space is a DOS. It is worth returning to dev_err()
> > >
> > > I think this should be dev_warn() unless you want to bring back the
> > > returning of errors on these conditions as well (i.e. as was the case
> > > prior to 0cb54a3e47cb ("USB: debugging code shouldn't alter control
> > > flow")).
> >
> > Should I? A warning in syslog is pretty hardcore, so I have no idea
> > whether dev_warn() is enough.
>
> Perhaps there are two sides to this. If something really should not be
> happening and needs to be addressed (i.e. it's a driver bug) that
> dev_WARN is warranted. If user space can be pass in bogus flags that
> gets propagated to USB core, perhaps those need to be sanitised sooner
> (in the vain of "don't trust anything coming from user space").
I'd go along with this. The usbfs code should fix or reject URBs
submitted from userspace with bogus flags or an incorrect pipe value.
(In fact, we already sanitize the flags to some extent, but we could do
more: ISO_ASAP should apply only to isochronous URBs, and ZERO_PACKET
should apply only to bulk-OUT URBS.)
Similar errors coming from kernel drivers should be reported as actual
bugs.
Alan
> In general though, I believe dev_warn() is more appropriate for cases
> where something odd is happening, but we try to recover and proceed
> anyway (e.g. by sanitising the flags without bailing out as is the case
> here) instead of aborting.
>
> Johan
