Re: [PATCH] kasan: fix slab double free when cpu-hotplug

[Andrew Morton]

On Fri, 11 Dec 2020 13:43:39 +0000 Chris Down <chris@xxxxxxxxxxxxxx> wrote:

> Hi folks,
> 
> Andrew Morton writes:
> >@@ -188,6 +190,10 @@ void quarantine_put(struct kasan_free_me
> > 	local_irq_save(flags);
> >
> > 	q = this_cpu_ptr(&cpu_quarantine);
> >+	if (q->offline) {
> >+		local_irq_restore(flags);
> >+		return;
> >+	}
> > 	qlist_put(q, &info->quarantine_link, cache->size);
> > 	if (unlikely(q->bytes > QUARANTINE_PERCPU_SIZE)) {
> > 		qlist_move_all(q, &temp);
> 
> I'm afraid as well as the issues already identified, this also fails, because 
> `quarantine_put` now returns a bool after "kasan: sanitize objects when 
> metadata doesn't fit":
> 
>      mm/kasan/quarantine.c: In function ‘quarantine_put’:
>      mm/kasan/quarantine.c:198:3: error: ‘return’ with no value, in function returning non-void [-Werror=return-type]
>        198 |   return;
>            |   ^~~~~~
>      mm/kasan/quarantine.c:171:6: note: declared here
>        171 | bool quarantine_put(struct kmem_cache *cache, void *object)

Yup, thanks.  I think I have this all fixed now, using the old
apply-one-patch-compile-everything-repeat approach.