Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler

Borislav Petkov
2021-02-05T13:59:36Z

On Wed, Feb 03, 2021 at 02:55:28PM -0800, Yu-cheng Yu wrote:
> +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
> +{
> + static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
> + DEFAULT_RATELIMIT_BURST);
> + struct task_struct *tsk;
> +
> + if (!user_mode(regs)) {
> + pr_emerg("PANIC: unexpected kernel control protection fault\n");
> + die("kernel control protection fault", regs, error_code);
> + panic("Machine halted.");
> + }
> +
> + cond_local_irq_enable(regs);
> +
> + if (!boot_cpu_has(X86_FEATURE_CET))
> + WARN_ONCE(1, "Control protection fault with CET support disabled\n");
> +
> + tsk = current;
> + tsk->thread.error_code = error_code;
> + tsk->thread.trap_nr = X86_TRAP_CP;
> +
> + if (show_unhandled_signals && unhandled_signal(tsk, SIGSEGV) &&
> + __ratelimit(&rs)) {

I can't find it written down anywhere why the ratelimiting is needed at
all?

--
Regards/Gruss,
Boris.