Re: [PATCH 6.12.y] cgroup: Fix kernfs_node UAF in css_free_rwork_fn

[T.J. Mercier]

On Fri, Jan 30, 2026 at 8:14 AM Michal Koutný <mkoutny@xxxxxxxx> wrote:
>
> On Thu, Jan 29, 2026 at 11:11:48AM -0800, "T.J. Mercier" <tjmercier@xxxxxxxxxx> wrote:
> > On Thu, Jan 29, 2026 at 11:10 AM T.J. Mercier <tjmercier@xxxxxxxxxx> wrote:
> > >
> > > This fix patch is not upstream, and is applicable only to kernels 6.10
> > > (where the cgroup_rstat_lock tracepoint was added) through 6.15 after
> > > which commit 5da3bfa029d6 ("cgroup: use separate rstat trees for each
> > > subsystem") reordered cgroup_rstat_flush as part of a new feature
> > > addition and inadvertently fixed this UAF.
> >
> > I am proposing we apply this one-off patch to stable rather than
> > backporting 5da3bfa029d6 ("cgroup: use separate rstat trees for each
> > subsystem") and its fixes to 6.12.y.
>
> That's a performance optimization rework, IMO too big for stable.
>
> For the conservative stable-specific fixup:
>
> Acked-by: Michal Koutný <mkoutny@xxxxxxxx>
>
> Thanks!

I forgot to thank you for your ack. So thanks Michal. :)

-T.J.