Re: [PATCH 2/2] debugfs: only allow root access to debugginginterfaces

[Hugh Dickins]

On Fri, 25 Feb 2011, Greg KH wrote:
> On Tue, Feb 22, 2011 at 11:29:15PM +0300, Dan Carpenter wrote:
> > On Tue, Feb 22, 2011 at 11:33:14AM -0800, Greg KH wrote:
> > > Again, let's fix the real problems here, world-writable debugfs files.
> > 
> > We could just ban them?
> > 
> > diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
> > index e7a7a2f..03ae095 100644
> > --- a/fs/debugfs/inode.c
> > +++ b/fs/debugfs/inode.c
> > @@ -223,6 +223,9 @@ struct dentry *debugfs_create_file(const char *name, mode_t mode,
> >  
> >  	pr_debug("debugfs: creating file '%s'\n",name);
> >  
> > +	/* don't allow world writable files */
> > +	mode &= ~S_IWOTH;
> > +
> >  	error = simple_pin_fs(&debug_fs_type, &debugfs_mount,
> >  			      &debugfs_mount_count);
> >  	if (error)
> > 
> 
> I have no objection to this patch, care to resend it with a
> signed-off-by: so that I can apply it?

That's funny, I wrote something in debugfs a few months ago which was
very deliberately rw--w--w-: a kind of circular trace buffer into which
any userspace could easily echo its progress for debugging.

Probably won't be upstreamed in that form, nor use debugfs if it is.
But I mention it as an example of why any such limitation on debugfs
seems inappropriate to me.

Hugh
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