Messages in this thread | | | Date | Sat, 27 Nov 2021 00:28:48 +0800 | From | Ming Lei <> | Subject | Re: [PATCH 1/2] kobject: don't delay to cleanup module kobject |
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On Fri, Nov 26, 2021 at 05:08:16PM +0100, Greg Kroah-Hartman wrote: > On Fri, Nov 05, 2021 at 02:37:09PM +0800, Ming Lei wrote: > > CONFIG_DEBUG_KOBJECT_RELEASE is used for debugging kobject release/cleanup > > issue. The module kobject is released after module_exit() returns. If > > this kobject is delayed too much, and may cause other kobject's > > cleaned up a bit earlier before freeing module, then real issue is > > hidden. > > > > So don't delay module kobject's cleanup, meantime module kobject is > > always cleaned up synchronously, and we needn't module kobject's > > cleanup. > > > > Signed-off-by: Ming Lei <ming.lei@redhat.com> > > --- > > lib/kobject.c | 5 +++++ > > 1 file changed, 5 insertions(+) > > > > diff --git a/lib/kobject.c b/lib/kobject.c > > index ea53b30cf483..4c0dbe11be3d 100644 > > --- a/lib/kobject.c > > +++ b/lib/kobject.c > > @@ -16,6 +16,7 @@ > > #include <linux/stat.h> > > #include <linux/slab.h> > > #include <linux/random.h> > > +#include <linux/module.h> > > > > /** > > * kobject_namespace() - Return @kobj's namespace tag. > > @@ -727,6 +728,10 @@ static void kobject_release(struct kref *kref) > > struct kobject *kobj = container_of(kref, struct kobject, kref); > > #ifdef CONFIG_DEBUG_KOBJECT_RELEASE > > unsigned long delay = HZ + HZ * (get_random_int() & 0x3); > > + > > + if (kobj->ktype == &module_ktype) > > + delay = 0; > > No, there should not be anything "special" about module kobjects to get > this kind of treatment. They should work like any other kobject and > clean up properly when needed.
Here setting 0 delay for module kobject is just for making DEBUG_KOBJECT_RELEASE reliable to detect/report issues. Otherwise if the random delay for module kobject is bigger than other kobjects, potential use-after-after won't be exposed.
Thanks, Ming
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