On Tue, Jan 9, 2024 at 4:51 PM Liam R. Howlett <Liam.Howlett@xxxxxxxxxx> wrote:
>
> * Paul E. McKenney <paulmck@xxxxxxxxxx> [240109 09:04]:
> > Hello!
> >
> > I get the splat shown below when running rcutorture on next-20240108
> > (and some less-recent -next versions) on scenarios that run KASAN and
> > that also enable CONFIG_DEBUG_LOCK_ALLOC=y. I am running gcc 8.5.0.
> >
> > Bisection fingers this commit:
> >
> > a414d4286f34 ("kasan: handle concurrent kasan_record_aux_stack calls")
> >
> > This commit does not appear to be trying to change the annotation
> > required of KASAN users, so I suspect that the commit is at fault. I am
> > including Liam in case Maple Tree is the bad guy, and should call_rcu()
> > need adjustment, here I am. ;-)
> >
> > Thoughts?
>
>
> I think this is ma_free_rcu() registering mt_free_rcu() in
> lib/maple_tree.c.
>
> The commit you point to saves and restores the irq state in
> __kasan_record_aux_stack(), but the trace below shows it is called prior
> to irqs being initialized. This isn't what lockdep is yelling about, so
> what am I missing? Maybe it will be caught after this issue is
> resolved?
Hm, I see a discrepancy in the KASAN code related to the guilty
commit. I believed it to be harmless, but perhaps it is not.
Paul, could you check if the attached patch fixes the issue for you?
This is rather a quick fix than a proper one, but let's see if this
one works.
Thanks!
diff --git a/mm/kasan/common.c b/mm/kasan/common.c
index 223af53d4338..0143c1b82004 100644
--- a/mm/kasan/common.c
+++ b/mm/kasan/common.c
@@ -208,10 +208,6 @@ static inline u8 assign_tag(struct kmem_cache *cache,
void * __must_check __kasan_init_slab_obj(struct kmem_cache *cache,
const void *object)
{
- /* Initialize per-object metadata if it is present. */
- if (kasan_requires_meta())
- kasan_init_object_meta(cache, object);
-
/* Tag is ignored in set_tag() without CONFIG_KASAN_SW/HW_TAGS */
object = set_tag(object, assign_tag(cache, object, true));
@@ -338,6 +334,10 @@ void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
if (is_kfence_address(object))
return (void *)object;
+ /* Initialize per-object metadata if it is present. */
+ if (kasan_requires_meta())
+ kasan_init_object_meta(cache, object);
+
/*
* Generate and assign random tag for tag-based modes.
* Tag is ignored in set_tag() for the generic mode.
