linux-kernel - Re: [PATCH V6 08/33] csky: Process management and Signal

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Date:   Thu, 27 Sep 2018 21:50:43 +0200
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     Guo Ren <ren_guo@...ky.com>
Cc:     akpm@...ux-foundation.org, arnd@...db.de,
        daniel.lezcano@...aro.org, davem@...emloft.net,
        gregkh@...uxfoundation.org, jason@...edaemon.net,
        marc.zyngier@....com, mark.rutland@....com,
        mchehab+samsung@...nel.org, peterz@...radead.org, robh@...nel.org,
        robh+dt@...nel.org, tglx@...utronix.de,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        devicetree@...r.kernel.org, green.hu@...il.com
Subject: Re: [PATCH V6 08/33] csky: Process management and Signal

Guo Ren <ren_guo@...ky.com> writes:

> --- /dev/null
> +++ b/arch/csky/abiv2/fpu.c
> +void fpu_fpe(struct pt_regs * regs)
> +{
> +	int sig;
> +	unsigned int fesr;
> +	siginfo_t info;
> +
> +	fesr = mfcr("cr<2, 2>");
> +
> +	if(fesr & FPE_ILLE){
> +		info.si_code = ILL_ILLOPC;
> +		sig = SIGILL;
> +	}
> +	else if(fesr & FPE_IDC){
> +		info.si_code = ILL_ILLOPN;
> +		sig = SIGILL;
> +	}
> +	else if(fesr & FPE_FEC){
> +		sig = SIGFPE;
> +		if(fesr & FPE_IOC){
> +			info.si_code = FPE_FLTINV;
> +		}
> +		else if(fesr & FPE_DZC){
> +			info.si_code = FPE_FLTDIV;
> +		}
> +		else if(fesr & FPE_UFC){
> +			info.si_code = FPE_FLTUND;
> +		}
> +		else if(fesr & FPE_OFC){
> +			info.si_code = FPE_FLTOVF;
> +		}
> +		else if(fesr & FPE_IXC){
> +			info.si_code = FPE_FLTRES;
> +		}
> +		else {
> +			info.si_code = NSIGFPE;
> +		}
> +	}
> +	else {
> +		info.si_code = NSIGFPE;
> +		sig = SIGFPE;
> +	}
> +	info.si_signo = SIGFPE;
> +	info.si_errno = 0;
> +	info.si_addr = (void *)regs->pc;
> +	force_sig_info(sig, &info, current);
> +}


This use of sending a signal is buggy.  It results in undefined values
being copied to userspace.

Userspace should never be sent NSIGXXX as a si_code.  You can use
FPE_FLTUNK for this default case.

In new code please use force_sig_fault instead of force_sig_info in new
code.  That saves you the trouble of messing with struct siginfo.

Thank you very much,
Eric Biederman