Messages in this thread Patch in this message | | | Date | Sun, 24 May 2020 15:28:12 +0200 | From | Greg Kroah-Hartman <> | Subject | Re: [PATCH] kobject: Make sure the parent does not get released before its children |
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On Sun, May 24, 2020 at 03:14:05PM +0200, Greg Kroah-Hartman wrote: > On Sun, May 24, 2020 at 02:57:27PM +0200, Greg Kroah-Hartman wrote: > > On Sat, May 23, 2020 at 08:44:06AM -0700, Randy Dunlap wrote: > > > On 5/23/20 8:36 AM, Greg Kroah-Hartman 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 > > > >> 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@linaro.org> > > > >> Reported-by: kernel test robot <rong.a.chen@intel.com> > > > >> Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"") > > > >> Suggested-by: "Rafael J. Wysocki" <rafael@kernel.org> > > > >> Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com> > > > >> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > >> Reviewed-by: Brendan Higgins <brendanhiggins@google.com> > > > >> Tested-by: Brendan Higgins <brendanhiggins@google.com> > > > >> Acked-by: Randy Dunlap <rdunlap@infradead.org> > > > >> --- > > > >> lib/kobject.c | 30 ++++++++++++++++++++---------- > > > >> 1 file changed, 20 insertions(+), 10 deletions(-) > > > > > > > > Stepping back, now that it turns out this patch causes more problems > > > > than it fixes, how is everyone reproducing the original crash here? > > > > > > Just load lib/test_printf.ko and boom! > > > > Thanks, that helps. > > > > Ok, in messing around with the kobject core more, originally we thought > > this was an issue of the kobject uevent happening for the parent pointer > > (when the parent was invalid). so, moving things around some more, and > > now I'm crashing in software_node_release() when we are trying to access > > swnode->parent->child_ids as parent is invalid there. > > > > So I feel like this is a swnode bug, or a use of swnode in a way it > > shouldn't be that the testing framework is exposing somehow. > > > > Let me dig deeper... > > Ah, ick, static software nodes trying to be cleaned up in the totally > wrong order. You can't just try to randomly clean up a kobject anywhere > in the middle of the hierarchy, that's flat out not going to work > properly. let me unwind it...
Ok, the patch below fixes the test, there's not really anything wrong with the kobject core, except maybe the kobject uevent for removal, which I'll send a patch for.
I'll write these up as a real set of patches after a bit.
thanks,
greg k-h
diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c index de8d3543e8fe..34bc2bbb3ada 100644 --- a/drivers/base/swnode.c +++ b/drivers/base/swnode.c @@ -715,14 +715,10 @@ EXPORT_SYMBOL_GPL(software_node_register_nodes); */ void software_node_unregister_nodes(const struct software_node *nodes) { - struct swnode *swnode; int i; - for (i = 0; nodes[i].name; i++) { - swnode = software_node_to_swnode(&nodes[i]); - if (swnode) - fwnode_remove_software_node(&swnode->fwnode); - } + for (i = 0; nodes[i].name; i++) + software_node_unregister(&nodes[i]); } EXPORT_SYMBOL_GPL(software_node_unregister_nodes); @@ -741,6 +737,20 @@ int software_node_register(const struct software_node *node) } EXPORT_SYMBOL_GPL(software_node_register); +/** + * software_node_unregister - Unregister static software node + * @node: The software node to be unregistered + */ +void software_node_unregister(const struct software_node *node) +{ + struct swnode *swnode; + + swnode = software_node_to_swnode(node); + if (swnode) + fwnode_remove_software_node(&swnode->fwnode); +} +EXPORT_SYMBOL_GPL(software_node_unregister); + struct fwnode_handle * fwnode_create_software_node(const struct property_entry *properties, const struct fwnode_handle *parent) diff --git a/include/linux/property.h b/include/linux/property.h index d86de017c689..0d4099b4ce1f 100644 --- a/include/linux/property.h +++ b/include/linux/property.h @@ -441,6 +441,7 @@ int software_node_register_nodes(const struct software_node *nodes); void software_node_unregister_nodes(const struct software_node *nodes); int software_node_register(const struct software_node *node); +void software_node_unregister(const struct software_node *node); int software_node_notify(struct device *dev, unsigned long action); diff --git a/lib/test_printf.c b/lib/test_printf.c index 6b1622f4d7c2..b320c733af70 100644 --- a/lib/test_printf.c +++ b/lib/test_printf.c @@ -637,7 +637,9 @@ static void __init fwnode_pointer(void) test(second_name, "%pfwP", software_node_fwnode(&softnodes[1])); test(third_name, "%pfwP", software_node_fwnode(&softnodes[2])); - software_node_unregister_nodes(softnodes); + software_node_unregister(&softnodes[2]); + software_node_unregister(&softnodes[1]); + software_node_unregister(&softnodes[0]); } static void __init
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