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

[Wang Dongsheng-B40534 <B40534@freescale.com>]

> -----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; linuxppc-dev@lists.ozlabs.org;
> Zhao Chenhui-B35336; Li Yang-R58472
> Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup support
>=20
> On 03/19/2013 10:48:53 PM, Wang Dongsheng-B40534 wrote:
> >
> >
> > > -----Original Message-----
> > > From: Wood Scott-B07421
> > > Sent: Wednesday, March 20, 2013 6:55 AM
> > > To: Wang Dongsheng-B40534
> > > Cc: Wood Scott-B07421; Gala Kumar-B11780;
> > 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 01:25:42 AM, Wang Dongsheng-B40534 wrote:
> > > > > -----Original Message-----
> > > > > From: Wood Scott-B07421
> > > > > Sent: Tuesday, March 19, 2013 8:31 AM
> > > > > To: Wang Dongsheng-B40534
> > > > > Cc: Gala Kumar-B11780; linuxppc-dev@lists.ozlabs.org; Wang
> > > > Dongsheng-
> > > > > B40534; Zhao Chenhui-B35336; Li Yang-R58472
> > > > > Subject: Re: [PATCH 3/3] powerpc/fsl: add MPIC timer wakeup
> > support
> > > > >
> > > > > On 03/08/2013 01:38:47 AM, Wang Dongsheng wrote:
> > > > > > +static ssize_t fsl_timer_wakeup_store(struct device *dev,
> > > > > > +				struct device_attribute *attr,
> > > > > > +				const char *buf,
> > > > > > +				size_t count)
> > > > > > +{
> > > > > > +	struct timeval interval;
> > > > > > +	int ret;
> > > > > > +
> > > > > > +	interval.tv_usec =3D 0;
> > > > > > +	if (kstrtol(buf, 0, &interval.tv_sec))
> > > > > > +		return -EINVAL;
> > > > >
> > > > > I don't think the buffer will NUL-terminated...  Ordinarily
> > > > there'll be
> > > > > an LF terminator, but you can't rely on that (many other sysfs
> > > > attributes
> > > > > seem to, though...).
> > > > >
> > > > I think we don't need to care about LF terminator.
> > > > The kstrtol--> _kstrtoull has been done.
> > >
> > > My point is, what happens if userspace passes in a buffer that has
> > no
> > > terminator of any sort?  kstrtol will continue reading beyond the
> > end of
> > > the buffer.
> > >
> > Do not care about terminator.
>=20
> kstrtol() obviously *does* because it doesn't take the buffer length as
> a parameter.
>=20
> > kstrtol--> _kstrtoull--> _parse_integer
> >
> > _kstrtoull(...) {
> > 	...
> > 	rv =3D _parse_integer(s, base, &_res);
> > 	if (rv & KSTRTOX_OVERFLOW)
> > 		return -ERANGE;
> > 	rv &=3D ~KSTRTOX_OVERFLOW;
> > 	if (rv =3D=3D 0)
> > 		return -EINVAL;
> > 	s +=3D rv;
> >
> > 	if (*s =3D=3D '\n')
> > 		s++;
> > 	if (*s)
> > 		return -EINVAL;
> > 	...
> > }
> >
> > _parse_integer(...) {
> > 	...
> > 	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.
>=20
> 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?
>=20
Under what case is unsafe, please make sense.

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