linux-kernel - Re: [PATCH v21 06/26] x86/cet: Add control-protection fault handler

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Date:   Wed, 24 Feb 2021 08:44:45 -0800
From:   "Yu, Yu-cheng" <yu-cheng.yu@...el.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Andy Lutomirski <luto@...nel.org>,
        Balbir Singh <bsingharora@...il.com>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Peter Zijlstra <peterz@...radead.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>,
        Weijiang Yang <weijiang.yang@...el.com>,
        Pengfei Xu <pengfei.xu@...el.com>,
        Haitao Huang <haitao.huang@...el.com>,
        Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [PATCH v21 06/26] x86/cet: Add control-protection fault handler

On 2/24/2021 8:13 AM, Borislav Petkov wrote:
> On Wed, Feb 17, 2021 at 02:27:10PM -0800, Yu-cheng Yu wrote:
>> +/*
>> + * 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);

[...]

>> +
>> +		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[err]);
>> +		print_vma_addr(KERN_CONT " in ", regs->ip);
>> +		pr_cont("\n");
>> +	}
>> +
>> +	force_sig_fault(SIGSEGV, SEGV_CPERR,
>> +			(void __user *)uprobe_get_trap_addr(regs));
> 
> Why is this calling an uprobes function?
> 

I will change it to error_get_trap_addr().

> Also, do not break that line even if it is longer than 80.
> 
>> +	cond_local_irq_disable(regs);
>> +}
>> +#endif
>> +
>>   static bool do_int3(struct pt_regs *regs)
>>   {
>>   	int res;
>> diff --git a/include/uapi/asm-generic/siginfo.h b/include/uapi/asm-generic/siginfo.h
>> index d2597000407a..1c2ea91284a0 100644
>> --- a/include/uapi/asm-generic/siginfo.h
>> +++ b/include/uapi/asm-generic/siginfo.h
>> @@ -231,7 +231,8 @@ typedef struct siginfo {
>>   #define SEGV_ADIPERR	7	/* Precise MCD exception */
>>   #define SEGV_MTEAERR	8	/* Asynchronous ARM MTE error */
>>   #define SEGV_MTESERR	9	/* Synchronous ARM MTE exception */
>> -#define NSIGSEGV	9
>> +#define SEGV_CPERR	10	/* Control protection fault */
>> +#define NSIGSEGV	10
> 
> I still don't see the patch adding this to the manpage of sigaction(2).
> 
> There's a git repo there: https://www.kernel.org/doc/man-pages/
> 
> and I'm pretty sure Michael takes patches.
> 

I will send a patch.

--
Yu-cheng