linux-kernel - Re: [PATCH] kobject: Access kobject name with caution if state is not initialized

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Date:   Mon, 20 Aug 2018 23:46:52 -0700
From:   Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH] kobject: Access kobject name with caution if state is
 not initialized

* Dmitry Torokhov <dmitry.torokhov@...il.com> [2018-08-20 12:33:50]:

> On Mon, Aug 20, 2018 at 12:22 PM Greg Kroah-Hartman
> <gregkh@...uxfoundation.org> wrote:
> >
> > On Mon, Aug 20, 2018 at 10:39:47PM +0530, Srikar Dronamraju wrote:
> > Lots of stupid modules can do dumb things.  Just don't do that.  The
> > kernel is not built to keep you from doing stupid things in kernel code
> > :)
> >
> > So I fail to see why this patch is needed.  What in-kernel code path is
> > trying to print a kobject's name before it is initialized?  Why not fix
> > that obvious bug instead of forcing the kernel core to protect from
> > stupid code?
> 
> Kay decided to add some guards in:
> 
> commit 0f4dafc0563c6c49e17fe14b3f5f356e4c4b8806
> Author: Kay Sievers <kay.sievers@...y.org>
> Date:   Wed Dec 19 01:40:42 2007 +0100
> 
>    Kobject: auto-cleanup on final unref
> ...
> 
> +       if (!kobj->state_initialized) {
> +               printk(KERN_ERR "kobject '%s' (%p): tried to add an "
> +                      "uninitialized object, something is seriously wrong.\n",
> +                      kobject_name(kobj), kobj);
> +               dump_stack();
> +               return -EINVAL;
> 
> Given that we have dump_stack() we can probably simply drop
> kobject_name(kobj) instead of building even more elaborate checks. Or
> just drop the whole check. Adding kobjects is somewhat uncommon
> operation, plus "gabage in, garbage out".
> 

Dropping the kobject_name(kobj) should also be okay.