Re: [External] Re: [PATCH v2] kprobes: Fix kill kprobe which has been marked as gone

[Muchun Song]

Hi Masami,

On Wed, Sep 2, 2020 at 11:05 AM Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:
>
> Hi Ingo,
>
> Could you merge this fix to -tip?

This patch has been merged into Andrew's mm tree.

>
> I can resend it with other kprobes fixes.
>
> Hi Muchun,
>
> We also need;
>
> Cc: stable@xxxxxxxxxxxxxxx
>
> for bugfix so that the patch can be backported correctly after merged to upstream.

Yeah, I got it. Thanks.

>
> Thank you,
>
> On Mon, 31 Aug 2020 10:59:19 +0800
> Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
>
> > Cc Andrew and Steven.
> >
> > Any other comments or someone can add this to the queue for the
> > merge window? It's worth fixing it.
> >
> > On Sat, Aug 22, 2020 at 11:01 AM Muchun Song <songmuchun@xxxxxxxxxxxxx> wrote:
> > >
> > > If a kprobe is marked as gone, we should not kill it again. Otherwise,
> > > we can disarm the kprobe more than once. In that case, the statistics
> > > of kprobe_ftrace_enabled can unbalance which can lead to that kprobe
> > > do not work.
> > >
> > > Fixes: e8386a0cb22f ("kprobes: support probing module __exit function")
> > > Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> > > Co-developed-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> > > Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
> > > Acked-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> > > ---
> > > changelogs in v2:
> > >  1. Add a WARN_ON_ONCE in the kill_kprobe() to catch incorrect use of it.
> > >  2. Update 'Fixes' tag in the commmit log.
> > >
> > >  kernel/kprobes.c | 9 ++++++++-
> > >  1 file changed, 8 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> > > index d36e2b017588..9348b0c36ae0 100644
> > > --- a/kernel/kprobes.c
> > > +++ b/kernel/kprobes.c
> > > @@ -2143,6 +2143,9 @@ static void kill_kprobe(struct kprobe *p)
> > >
> > >         lockdep_assert_held(&kprobe_mutex);
> > >
> > > +       if (WARN_ON_ONCE(kprobe_gone(p)))
> > > +               return;
> > > +
> > >         p->flags |= KPROBE_FLAG_GONE;
> > >         if (kprobe_aggrprobe(p)) {
> > >                 /*
> > > @@ -2422,7 +2425,10 @@ static int kprobes_module_callback(struct notifier_block *nb,
> > >         mutex_lock(&kprobe_mutex);
> > >         for (i = 0; i < KPROBE_TABLE_SIZE; i++) {
> > >                 head = &kprobe_table[i];
> > > -               hlist_for_each_entry(p, head, hlist)
> > > +               hlist_for_each_entry(p, head, hlist) {
> > > +                       if (kprobe_gone(p))
> > > +                               continue;
> > > +
> > >                         if (within_module_init((unsigned long)p->addr, mod) ||
> > >                             (checkcore &&
> > >                              within_module_core((unsigned long)p->addr, mod))) {
> > > @@ -2439,6 +2445,7 @@ static int kprobes_module_callback(struct notifier_block *nb,
> > >                                  */
> > >                                 kill_kprobe(p);
> > >                         }
> > > +               }
> > >         }
> > >         if (val == MODULE_STATE_GOING)
> > >                 remove_module_kprobe_blacklist(mod);
> > > --
> > > 2.11.0
> > >
> >
> >
> > --
> > Yours,
> > Muchun
>
>
> --
> Masami Hiramatsu <mhiramat@xxxxxxxxxx>



-- 
Yours,
Muchun