linux-kernel - Re: [PATCH] kobject: Make sure the parent does not get released before its children

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Date:   Sat, 23 May 2020 16:04:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        linux-kernel@...r.kernel.org,
        Naresh Kamboju <naresh.kamboju@...aro.org>,
        kernel test robot <rong.a.chen@...el.com>,
        Brendan Higgins <brendanhiggins@...gle.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [PATCH] kobject: Make sure the parent does not get released
 before its children

On Sat, May 23, 2020 at 06:21:01AM -0700, Guenter Roeck wrote:
> On Wed, May 13, 2020 at 06:18:40PM +0300, Heikki Krogerus wrote:
> > In the function kobject_cleanup(), kobject_del(kobj) is
> > called before the kobj->release(). That makes it possible to
> > release the parent of the kobject before the kobject itself.
> > 
> > To fix that, adding function __kboject_del() that does
> 
> s/kboject/kobject/
> 
> > everything that kobject_del() does except release the parent
> > reference. kobject_cleanup() then calls __kobject_del()
> > instead of kobject_del(), and separately decrements the
> > reference count of the parent kobject after kobj->release()
> > has been called.
> > 
> > Reported-by: Naresh Kamboju <naresh.kamboju@...aro.org>
> > Reported-by: kernel test robot <rong.a.chen@...el.com>
> > Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"")
> > Cc: Brendan Higgins <brendanhiggins@...gle.com>
> > Cc: Randy Dunlap <rdunlap@...radead.org>
> > Suggested-by: "Rafael J. Wysocki" <rafael@...nel.org>
> > Signed-off-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
> > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > Reviewed-by: Brendan Higgins <brendanhiggins@...gle.com>
> > Tested-by: Brendan Higgins <brendanhiggins@...gle.com>
> > Acked-by: Randy Dunlap <rdunlap@...radead.org>
> > Tested-by: Randy Dunlap <rdunlap@...radead.org>
> 
> All my arm64be (arm64 big endian) boot tests crash with this patch
> applied. Reverting it fixes the problem. Crash log and bisect results
> (from pending-fixes branch) below.

Ugh, ok, just when I send Linus a pull request.  Let me go fix that...

greg k-h