linux-kernel - RE: [PATCH V2] [X86] Fix potential issue on memmove

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Date:	Thu, 12 Aug 2010 14:52:38 +0800
From:	"Ma, Ling" <ling.ma@...el.com>
To:	Namhyung Kim <namhyung@...il.com>
CC:	"hpa@...or.com" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"mingo@...e.hu" <mingo@...e.hu>
Subject: RE: [PATCH V2] [X86] Fix potential issue on memmove

Thanks, I will fix it in next version.

> -----Original Message-----
> From: Namhyung Kim [mailto:namhyung@...il.com]
> Sent: Thursday, August 12, 2010 2:49 PM
> To: Ma, Ling
> Cc: hpa@...or.com; tglx@...utronix.de; linux-kernel@...r.kernel.org;
> mingo@...e.hu
> Subject: Re: [PATCH V2] [X86] Fix potential issue on memmove
> 
> > --- a/arch/x86/lib/memcpy_32.c
> > +++ b/arch/x86/lib/memcpy_32.c
> > @@ -25,19 +25,35 @@ void *memmove(void *dest, const void *src, size_t
> n)
> >	int d0, d1, d2;
> >
> > 	if (dest < src) {
> > -		memcpy(dest, src, n);
> > +		if ((dest + n) < src)
> > +			 return memcpy(dest, src, n);
> > +		else
> > +			__asm__ __volatile__(
> > +				"rep\n\t"
> > +				"movsb\n\t"
> > +				: "=&c" (d0), "=&S" (d1), "=&D" (d2)
> > +				:"0" (n),
> > +				 "1" (src),
> > +				 "2" (dest)
> > +				:"memory");
> > +
> > 	} else {
> > -		__asm__ __volatile__(
> > -			"std\n\t"
> > -			"rep\n\t"
> > -			"movsb\n\t"
> > -			"cld"
> > -			: "=&c" (d0), "=&S" (d1), "=&D" (d2)
> > -			:"0" (n),
> > -			 "1" (n-1+src),
> > -			 "2" (n-1+dest)
> > -			:"memory");
> > +		if((src + count) < dest)
> > +			return memcpy(dest, src, count);
> 
> 'count' should be 'n'.
> 
> --
> Regards,
> Namhyung Kim
>