Re: uprobes: memory leak in enable/disable loop

[Oleg Nesterov]

On 08/16, Oleg Nesterov wrote:
>
> On 08/15, Brenden Blanco wrote:
> >
> > Hi folks,
> >
> > I think I have come across a memory leak in uprobes, which is fairly easy to
> > reproduce.
>
> At first glance this looks as a problem in memcg, add CC's...
>
> put_page(old_page) looks properly balanced, and I assume we do not need
> the additional "uncharge", we can rely on __page_cache_release().
>
> And I do not see any leak if I try to reproduce with CONFIG_MEMCG=n.

Heh. it seems that mem_cgroup_*() logic was always wrong in __replace_page().

Could you try the patch below?

Oleg.
---

--- x/kernel/events/uprobes.c
+++ x/kernel/events/uprobes.c
@@ -200,7 +200,8 @@ static int __replace_page(struct vm_area
 
 	err = 0;
  unlock:
-	mem_cgroup_cancel_charge(kpage, memcg, false);
+ 	if (err)
+		mem_cgroup_cancel_charge(kpage, memcg, false);
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 	unlock_page(page);
 	return err;