Re: [PATCH v17 06/26] x86/cet: Add control-protection fault handler

[Yu, Yu-cheng]

On 1/19/2021 4:04 AM, Borislav Petkov wrote:
> On Tue, Dec 29, 2020 at 01:30:33PM -0800, Yu-cheng Yu wrote:
[...]
> > +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
> > +{
> > +	struct task_struct *tsk;
> > +
> > +	if (!user_mode(regs)) {
> > +		if (notify_die(DIE_TRAP, "control protection fault", regs,
> > +			       error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP)
> > +			return;
> > +		die("Upexpected/unsupported kernel control protection fault", regs, error_code);
>
> Isn't the machine supposed to panic() here and do no further progress?

Ok, make it panic().

> > +	}
> > +
> > +	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) &&
> > +	    printk_ratelimit()) {
>
> WARNING: Prefer printk_ratelimited or pr_<level>_ratelimited to printk_ratelimit
> #136: FILE: arch/x86/kernel/traps.c:645:
> +	    printk_ratelimit()) {
>
> Still not using checkpatch?

Most places in arch/x86 still use printk_ratelimit().  I should have 
trusted checkpatch.  I will fix it.

> > +		unsigned int max_err;
> > +		unsigned long ssp;
> > +
> > +		max_err = ARRAY_SIZE(control_protection_err) - 1;
> > +		if ((error_code < 0) || (error_code > max_err))
> > +			error_code = 0;
> > +
> > +		rdmsrl(MSR_IA32_PL3_SSP, ssp);
> > +		pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)",
>
> If anything, all this stuff should be pr_emerg().

I will fix it.

--
Yu-cheng