Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support

[Scott Wood <scottwood@freescale.com>]

On 03/22/2013 12:46:24 AM, Wang Dongsheng-B40534 wrote:
>=20
>=20
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Thursday, March 21, 2013 5:49 AM
> > To: Wang Dongsheng-B40534
> > Cc: Wood Scott-B07421; Gala Kumar-B11780; =20
> linuxppc-dev@lists.ozlabs.org;
> > Zhao Chenhui-B35336; Li Yang-R58472
> > Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support
> >
> > On 03/19/2013 10:48:53 PM, Wang Dongsheng-B40534 wrote:
> > > 	while (*s) {
> > > 		if ('0' <=3D *s && *s <=3D '9')
> > > 			val =3D *s - '0';
> > > 		else if ('a' <=3D _tolower(*s) && _tolower(*s) <=3D 'f')
> > > 			val =3D _tolower(*s) - 'a' + 10;
> > > 		else
> > > 			break;	//this will break out to convert.
> >
> > Really?  How do you know that the next byte after the buffer isn't a
> > valid hex digit?  How do you even know that we won't take a fault
> > accessing it?
> >
> Under what case is unsafe, please make sense.

char buffer[1] =3D { '5' };
write(fd, &buffer, 1);

What comes after that '5' byte in the pointer you pass to kstrtol?

> "kstrtol" is used in almost of sysfs interface, I think it should be =20
> accepted in defaule :).

Just because a lot of other people copy blindly doesn't make it right.  =20
Most of the examples I found use sscanf instead, though that has the =20
same problem.

I do see a few instances of the "strings from sysfs write are not 0 =20
terminated!" in the comments, though (kernel/time/clocksource.c and =20
kernel/rtmutex-tester.c).

Also "words written to sysfs files may, or may not, be \n terminated" =20
in drivers/md/md.c.

-Scott=