Re: kernel panic: Attempted to kill init!

[Alexei Starovoitov]

On Thu, Jan 5, 2023 at 1:00 AM Hao Sun <sunhao.th@xxxxxxxxx> wrote:
> >
> > Does syzbot running without any user space?
> > Is syzbot itself a pid=1 ? and the only process ?
> > If so, the error would makes sense.
>
> Yes, after read the C reproducer again, noticed that after a
> bunch of sandbox setup, the pid of the reproducer process at
> runtime is 1.
>
> > I guess we can add a safety check to bpf_send_signal_common
> > to prevent syzbot from killing itself.
>
> Maybe something like this? This can avoid the panic, but won’t
> allow task with pid=1 to send signal with prog.
>
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 23ce498bca97..94d2af2ce433 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -844,6 +844,8 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
>          */
>         if (unlikely(current->flags & (PF_KTHREAD | PF_EXITING)))
>                 return -EPERM;
> +       if (unlikely(is_global_init(current)))
> +               return -EPERM;
>         if (unlikely(!nmi_uaccess_okay()))
>                 return -EPERM;

Yep. Good idea. Pls send an official patch.