Re: [PATCH] mm: memcg/slab: fix racy access to page->mem_cgroup in mem_cgroup_from_obj()

[Shakeel Butt]

On Fri, Sep 11, 2020 at 2:34 PM Roman Gushchin <guro@xxxxxx> wrote:
>
[snip]
> >
> > Also have you taken a look at [1]? I am still trying to figure out how
> > that is possible.
> >
> > [1] https://lore.kernel.org/lkml/20200901075321.GL4299@shao2-debian/
>
> Hm, yeah, it's complicated. At the very first glance it looks like that the
> obj_cgroups vector is placed onto the very same page it describes, or at least
> it shares the kmem_cache with it, with some bad consequences. Could be something
> SLAB-specific, newer saw anything like that with SLUB.
> Or maybe it's completely unrelated and has been attributed to this commit
> by mistake.
>
> I've spent several hours running the provided test in a loop, but wasn't
> lucky enough to trigger it. Did you try?
>

Yeah same, no success in reproducing it.