Re: [PATCH v15 04/26] x86/cet: Add control-protection fault handler

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Tue, Nov 10, 2020 at 08:21:49AM -0800, Yu-cheng Yu wrote:
> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> index e19df6cde35d..6c21c1e92605 100644
> --- a/arch/x86/kernel/traps.c
> +++ b/arch/x86/kernel/traps.c
> @@ -598,6 +598,65 @@ DEFINE_IDTENTRY_ERRORCODE(exc_general_protection)
>  	cond_local_irq_disable(regs);
>  }
>  
> +#ifdef CONFIG_X86_CET
> +static const char * const control_protection_err[] = {
> +	"unknown",
> +	"near-ret",
> +	"far-ret/iret",
> +	"endbranch",
> +	"rstorssp",
> +	"setssbsy",
> +};
> +
> +/*
> + * When a control protection exception occurs, send a signal
> + * to the responsible application.  Currently, control
> + * protection is only enabled for the user mode.  This
> + * exception should not come from the kernel mode.
> + */

Make that 80 cols wide.

> +DEFINE_IDTENTRY_ERRORCODE(exc_control_protection)
> +{
> +	struct task_struct *tsk;
> +
> +	if (notify_die(DIE_TRAP, "control protection fault", regs,
> +		       error_code, X86_TRAP_CP, SIGSEGV) == NOTIFY_STOP)
> +		return;

What is the intent here, notifiers can prevent the machine from printing
the CP error below?

> +	cond_local_irq_enable(regs);
> +
> +	if (!user_mode(regs))
> +		die("kernel control protection fault", regs, error_code);

Let's write that more explicitly:

		die("Unexpected/unsupported control protection fault"...

> +
> +	if (!static_cpu_has(X86_FEATURE_SHSTK) &&
> +	    !static_cpu_has(X86_FEATURE_IBT))

Why static_cpu_has?

> +		WARN_ONCE(1, "CET is disabled but got control protection fault\n");

			     "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()) {
> +		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;

<---- newline here.

> +		rdmsrl(MSR_IA32_PL3_SSP, ssp);
> +		pr_info("%s[%d] control protection ip:%lx sp:%lx ssp:%lx error:%lx(%s)",
> +			tsk->comm, task_pid_nr(tsk),
> +			regs->ip, regs->sp, ssp, error_code,
> +			control_protection_err[error_code]);
> +		print_vma_addr(KERN_CONT " in ", regs->ip);
> +		pr_cont("\n");
> +	}

...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette



[Index of Archives]     [Linux Kernel]     [Kernel Newbies]     [x86 Platform Driver]     [Netdev]     [Linux Wireless]     [Netfilter]     [Bugtraq]     [Linux Filesystems]     [Yosemite Discussion]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Samba]     [Device Mapper]

  Powered by Linux