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

[Masami Hiramatsu <mhiramat@kernel.org>]

Hi Ingo,

Could you merge this fix to -tip?

I can resend it with other kprobes fixes.

Hi Muchun,

We also need;

Cc: stable@vger.kernel.org

for bugfix so that the patch can be backported correctly after merged to upstream.

Thank you,

On Mon, 31 Aug 2020 10:59:19 +0800
Muchun Song <songmuchun@bytedance.com> 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@bytedance.com> 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@bytedance.com>
> > Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
> > Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> > Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
> > ---
> > 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@kernel.org>