Messages in this thread |  | | Subject | Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler | From | "Yu, Yu-cheng" <> | Date | Fri, 5 Feb 2021 10:00:21 -0800 |
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On 2/5/2021 5:59 AM, Borislav Petkov wrote: > 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? >
The ratelimit here is only for #CP, and its rate is not counted together with other types of faults. If a task gets here, it will exit. The only condition the ratelimit will trigger is when multiple tasks hit #CP at once, which is unlikely. Are you suggesting that we do not need the ratelimit here?
Thanks!
-- Yu-cheng
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