Re: [PATCH] kernfs: Move faulting copy_user operations outside of the mutex

[Greg Kroah-Hartman]

On Thu, Mar 31, 2016 at 08:30:05PM +0300, Joonas Lahtinen wrote:
> On to, 2016-03-31 at 12:49 -0400, Tejun Heo wrote:
> > On Thu, Mar 31, 2016 at 11:45:06AM +0100, Chris Wilson wrote:
> > > 
> > > A fault in a user provided buffer may lead anywhere, and lockdep warns
> > > that we have a potential deadlock between the mm->mmap_sem and the
> > > kernfs file mutex:
> > ...
> > > 
> > > Reported-by: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > > Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94350
> > > Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> > > Reviewed-by: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > > Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
> > > Cc: Joonas Lahtinen <joonas.lahtinen@xxxxxxxxxxxxxxx>
> > > Cc: Tejun Heo <tj@xxxxxxxxxx>
> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> > > Cc: NeilBrown <neilb@xxxxxxx>
> > > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Acked-by: Tejun Heo <tj@xxxxxxxxxx>
> > 
> 
> Thanks.
> 
> I have applied this locally to our repo to be included into our CI
> builds.
> 
> We will drop the local patch once this waterfalls from upstream to our
> drm-intel-nightly repo.

So is this something that needs to get into 4.6-final because it
resolves a reported issue?  Or can it wait for 4.7-rc1?

thanks,

greg k-h