linux-kernel - Re: [PATCH] kprobe: reverse kp->flags when arm

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Date:   Thu, 15 Sep 2022 15:04:17 +0800
From:   Li Qiang <liq3ea@...il.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     Li Qiang <liq3ea@....com>, naveen.n.rao@...ux.ibm.com,
        anil.s.keshavamurthy@...el.com, davem@...emloft.net,
        linux-kernel@...r.kernel.org, Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [PATCH] kprobe: reverse kp->flags when arm_kprobe failed

Masami Hiramatsu <mhiramat@...nel.org> 于2022年9月9日周五 21:07写道：
>
> On Fri,  2 Sep 2022 08:58:20 -0700
> Li Qiang <liq3ea@....com> wrote:
>
> > In aggregate kprobe case, when arm_kprobe failed,
> > we need set the kp->flags with KPROBE_FLAG_DISABLED again.
> > If not, the 'kp' kprobe will been considered as enabled
> > but it actually not enabled.
> >
> > Signed-off-by: Li Qiang <liq3ea@....com>
>
> Looks good to me.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>


Hello Masami,

Who should merge this,  you? This issue will crash the kernel before:

0bc11ed5ab60c135aa764a62c02cd5ea68289de4 commit ("kprobes: Allow
kprobes coexist with
livepatch") and
8094029330a2f03fb406ecff80671cf27ce28d42 commit("libbpf: Cleanup the
legacy kprobe_event on failed add/attach_event()")

Thanks,
Li Qiang

>
> Thanks!
>
> > ---
> >  kernel/kprobes.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > index 08350e35a..333454df5 100644
> > --- a/kernel/kprobes.c
> > +++ b/kernel/kprobes.c
> > @@ -2424,8 +2424,11 @@ int enable_kprobe(struct kprobe *kp)
> >       if (!kprobes_all_disarmed && kprobe_disabled(p)) {
> >               p->flags &= ~KPROBE_FLAG_DISABLED;
> >               ret = arm_kprobe(p);
> > -             if (ret)
> > +             if (ret) {
> >                       p->flags |= KPROBE_FLAG_DISABLED;
> > +                     if (p != kp)
> > +                             kp->flags |= KPROBE_FLAG_DISABLED;
> > +             }
> >       }
> >  out:
> >       mutex_unlock(&kprobe_mutex);
> > --
> > 2.25.1
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@...nel.org>