Re: [RFC PATCH v10 mm-new 6/9] bpf: mark mm->owner as __safe_rcu_or_null

[Yafang Shao <laoar.shao@gmail.com>]

On Thu, Oct 16, 2025 at 12:36 AM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Wed, Oct 15, 2025 at 7:18 AM Yafang Shao <laoar.shao@gmail.com> wrote:
> >
> > When CONFIG_MEMCG is enabled, we can access mm->owner under RCU. The
> > owner can be NULL. With this change, BPF helpers can safely access
> > mm->owner to retrieve the associated task from the mm. We can then make
> > policy decision based on the task attribute.
> >
> > The typical use case is as follows,
> >
> >   bpf_rcu_read_lock(); // rcu lock must be held for rcu trusted field
> >   @owner = @mm->owner; // mm_struct::owner is rcu trusted or null
> >   if (!@owner)
> >       goto out;
> >
> >   /* Do something based on the task attribute */
> >
> > out:
> >   bpf_rcu_read_unlock();
> >
> > Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> > Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> > Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> > ---
> >  kernel/bpf/verifier.c | 3 +++
> >  1 file changed, 3 insertions(+)
> >
>
> I thought you were going to send this and next patches outside of your
> thp patch set to land them sooner, as they don't have dependency on
> the rest of the patches and are useful on their own?

Thanks for your reminder.
They have been sent separately:

  https://lore.kernel.org/bpf/20251016063929.13830-1-laoar.shao@gmail.com/

-- 
Regards
Yafang