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From:   Li Qiang <liq3ea@gmail.com>
Date:   Thu, 15 Sep 2022 15:04:17 +0800
Message-ID: <CAKXe6SLNaWknvTdqPb0aGWtbQgp0mJz28KpRMZgwbdXV1DQ=wQ@mail.gmail.com>
Subject: Re: [PATCH] kprobe: reverse kp->flags when arm_kprobe failed
To:     Masami Hiramatsu <mhiramat@kernel.org>
Cc:     Li Qiang <liq3ea@163.com>, naveen.n.rao@linux.ibm.com,
        anil.s.keshavamurthy@intel.com, davem@davemloft.net,
        linux-kernel@vger.kernel.org, Steven Rostedt <rostedt@goodmis.org>
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Masami Hiramatsu <mhiramat@kernel.org> =E4=BA=8E2022=E5=B9=B49=E6=9C=889=E6=
=97=A5=E5=91=A8=E4=BA=94 21:07=E5=86=99=E9=81=93=EF=BC=9A
>
> On Fri,  2 Sep 2022 08:58:20 -0700
> Li Qiang <liq3ea@163.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@163.com>
>
> Looks good to me.
>
> Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.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 &=3D ~KPROBE_FLAG_DISABLED;
> >               ret =3D arm_kprobe(p);
> > -             if (ret)
> > +             if (ret) {
> >                       p->flags |=3D KPROBE_FLAG_DISABLED;
> > +                     if (p !=3D kp)
> > +                             kp->flags |=3D KPROBE_FLAG_DISABLED;
> > +             }
> >       }
> >  out:
> >       mutex_unlock(&kprobe_mutex);
> > --
> > 2.25.1
> >
>
>
> --
> Masami Hiramatsu (Google) <mhiramat@kernel.org>