Re: [PATCH v2] inode: debugfs_create_dir uses mode permission from parent

[Greg KH]

On Mon, Apr 30, 2018 at 04:15:58PM +0200, Jann Horn wrote:
> On Fri, Apr 27, 2018 at 3:49 PM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
> > I'm going to add Kees and the kernel-hardning list here, as I'd like
> > their opinions for the patch below.
> >
> > Kees, do you have any problems with this patch?  I know you worked on
> > making debugfs more "secure" from non-root users, this should still keep
> > the intial mount permissions all fine, right?  Anything I'm not
> > considering here?
> >
> > thanks,
> >
> > greg k-h
> >
> > On Fri, Apr 27, 2018 at 02:35:47PM +0200, Thomas Richter wrote:
> >> Currently function debugfs_create_dir() creates a new
> >> directory in the debugfs (usually mounted /sys/kernel/debug)
> >> with permission rwxr-xr-x. This is hard coded.
> >>
> >> Change this to use the parent directory permission.
> 
> AFAICS no inodes in debugfs have handlers for the ->rename, ->mkdir,
> ->create inode ops. What is write permission on debugfs directories
> useful for?

I doubt anything :)