Re: [PATCH] uprobes: Fix NULL pointer dereference in hprobe_expire()

[Andrii Nakryiko]

On Wed, Jul 29, 2026 at 9:02 AM Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> On 07/29, Breno Leitao wrote:
> >
> > --- a/kernel/events/uprobes.c
> > +++ b/kernel/events/uprobes.c
> > @@ -832,7 +832,7 @@ static struct uprobe *hprobe_expire(struct hprobe *hprobe, bool get)
> >               if (try_cmpxchg(&hprobe->state, &hstate, uprobe ? HPROBE_STABLE : HPROBE_GONE)) {
> >                       /* We won the race, we are the ones to unlock SRCU */
> >                       __srcu_read_unlock(&uretprobes_srcu, hprobe->srcu_idx);
> > -                     return get ? get_uprobe(uprobe) : uprobe;
> > +                     return get && uprobe ? get_uprobe(uprobe) : uprobe;
>
> Well, looks "obviously correct". At least the current code is obviously
> wrong, it even checks uprobe != NULL 3 lines above.
>
> Andrii ?
>

Yes, indeed, I'm more surprised this didn't come up much earlier
(probably it's rare enough to have uretprobe with refcnt at zero
during fork). The fix looks good, thanks!

Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>

> Acked-by: Oleg Nesterov <oleg@xxxxxxxxxx>
>
>