Re: [Merge tag 'pci-v4.12-changes' of git] 857f864014: BUG: unable to handle kernel NULL pointer dereference at 00000000000000a8

Greg Kroah-Hartman
2017-06-14T05:01:24Z

On Tue, Jun 13, 2017 at 09:13:32PM +0200, Sven-Haegar Koch wrote:
> On Tue, 13 Jun 2017, Greg Kroah-Hartman wrote:
>
> > On Tue, Jun 13, 2017 at 10:25:40AM -0600, Logan Gunthorpe wrote:
> > >
> > > On 12/06/17 10:35 PM, Greg Kroah-Hartman wrote:
> > > > Or better yet, just turn all char major allocations into dynamic, which
> > > > would be really good for test systems. I thought someone proposed
> > > > patches for that a long time ago, but I can't find them anymore. That
> > > > would be the simplest solution here.
> > >
> > > Would people not complain about that? I would not be surprised if some
> > > crazy application is using hard coded major numbers in userspace. So
> > > such a change could potentially break userspace...
> >
> > For char devices, I doubt it, but we can't take the chance, which is why
> > you make it an option. Then, it's enabled for 'allmodconfig' builds,
> > which helps testers out.
>
> At least for /dev/null, /dev/zero, and perhaps /dev/tty it would
> definitely break things if the major+minor number is not static. I have
> multiple chroot environments having only some minimal needed static
> /dev subdir, with naturally no daemons or filesystem creating those
> on-demand. For the main /dev I use whatever the system sets up, so
> devtmpfs with udev.

No, it wouldn't be required, it would be an option for those people
using devtmpfs.

thanks,

greg k-h