Messages in this thread |  | | Subject | Re: [PATCH v19 06/25] x86/cet: Add control-protection fault handler | From | "Yu, Yu-cheng" <> | Date | Thu, 4 Feb 2021 16:10:13 -0800 |
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On 2/4/2021 12:09 PM, Kees Cook wrote: > On Wed, Feb 03, 2021 at 02:55:28PM -0800, Yu-cheng Yu wrote:
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>> diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c >> index 7f5aec758f0e..f5354c35df32 100644 >> --- a/arch/x86/kernel/traps.c >> +++ b/arch/x86/kernel/traps.c >> @@ -606,6 +606,66 @@ 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 user mode. >> + * This exception should not come from kernel mode. >> + */ >> +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)) { >> + 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; > > Do you want to mask the error_code here before printing its value? > >> + >> + rdmsrl(MSR_IA32_PL3_SSP, ssp); >> + pr_emerg("%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]); > > Instead, you could clamp error_code to ARRAY_SIZE(control_protection_err), > and add another "unknown" to the end of the strings: > > control_protection_err[ > array_index_nospec(error_code, > ARRAY_SIZE(control_protection_err))] > > Everything else looks good. >
I will update it. Thanks!
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