Re: [PATCH -tip 5/5] kprobes: Don't call BUG_ON if there is a kprobe in use on free list

From: Ingo Molnar
Date: Mon Sep 10 2018 - 08:24:03 EST



* Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote:

> Instead of calling BUG_ON, if we find a kprobe in use on free kprobe
> list, just remove it from the list and keep it on kprobe hash list
> as same as other in-use kprobes.
>
> Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
> ---
> kernel/kprobes.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/kprobes.c b/kernel/kprobes.c
> index 63c342e5e6c3..e3420364b415 100644
> --- a/kernel/kprobes.c
> +++ b/kernel/kprobes.c
> @@ -546,8 +546,14 @@ static void do_free_cleaned_kprobes(void)
> struct optimized_kprobe *op, *tmp;
>
> list_for_each_entry_safe(op, tmp, &freeing_list, list) {
> - BUG_ON(!kprobe_unused(&op->kp));
> list_del_init(&op->list);
> + if (!kprobe_unused(&op->kp)) {
> + /*
> + * This must not happen, but if there is a kprobe
> + * still in use, keep it on kprobes hash list.
> + */
> + continue;

If this is an 'impossible' code path then I think it would make sense to add a WARN_ON_ONCE()
here.

Thanks,

Ingo