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Date:   Fri, 5 Feb 2021 13:06:16 +0800
From:   Aili Yao <yaoaili@kingsoft.com>
To:     "HORIGUCHI =?UTF-8?B?TkFPWUE=?=(=?UTF-8?B?5aCA5Y+j44CA55u05Lmf?=)" 
        <naoya.horiguchi@nec.com>
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Subject: Re: [PATCH v2] x86/fault: Send a SIGBUS to user process always for
 hwpoison page access.
Message-ID: <20210205130616.6d876846@alex-virtual-machine>
In-Reply-To: <20210204072555.GA22850@hori.linux.bs1.fc.nec.co.jp>
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        <20210204072555.GA22850@hori.linux.bs1.fc.nec.co.jp>
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On Thu, 4 Feb 2021 07:25:55 +0000
HORIGUCHI NAOYA(堀口　直也) <naoya.horiguchi@nec.com> wrote:

> Hi Aili,
> 
> On Mon, Feb 01, 2021 at 04:17:49PM +0800, Aili Yao wrote:
> > When one page is already hwpoisoned by AO action, process may not be
> > killed, the process mapping this page may make a syscall include this
> > page and result to trigger a VM_FAULT_HWPOISON fault, if it's in kernel
> > mode it may be fixed by fixup_exception. Current code will just return
> > error code to user process.
> > 
> > This is not sufficient, we should send a SIGBUS to the process and log
> > the info to console, as we can't trust the process will handle the error
> > correctly.
> > 
> > Suggested-by: Feng Yang <yangfeng1@kingsoft.com>
> > Signed-off-by: Aili Yao <yaoaili@kingsoft.com>
> > ---  
> ...
> 
> > @@ -662,12 +662,32 @@ no_context(struct pt_regs *regs, unsigned long error_code,
> >  		 * In this case we need to make sure we're not recursively
> >  		 * faulting through the emulate_vsyscall() logic.
> >  		 */
> > +
> > +		if (IS_ENABLED(CONFIG_MEMORY_FAILURE) &&
> > +		    fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
> > +			unsigned int lsb = 0;
> > +
> > +			pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
> > +				current->comm, current->pid, address);
> > +
> > +			sanitize_error_code(address, &error_code);
> > +			set_signal_archinfo(address, error_code);
> > +
> > +			if (fault & VM_FAULT_HWPOISON_LARGE)
> > +				lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
> > +			if (fault & VM_FAULT_HWPOISON)
> > +				lsb = PAGE_SHIFT;
> > +
> > +			force_sig_mceerr(BUS_MCEERR_AR, (void __user *)address, lsb);  
> 
> This part contains some duplicated code with do_sigbus(), so some refactoring (like
> adding a common function) would be more helpful.

Yes, agree, I will modify this and rebase to the big fault series from tip.

Thanks
Aili Yao