Re: [PATCH v4 2/4] lib: vsprintf: Fix handling of number field widths in vsscanf

[Richard Fitzgerald]

On 04/02/2021 16:35, Petr Mladek wrote:
> On Wed 2021-02-03 21:45:55, Andy Shevchenko wrote:
> > On Wed, Feb 03, 2021 at 04:50:07PM +0000, Richard Fitzgerald wrote:
> > > The existing code attempted to handle numbers by doing a strto[u]l(),
> > > ignoring the field width, and then repeatedly dividing to extract the
> > > field out of the full converted value. If the string contains a run of
> > > valid digits longer than will fit in a long or long long, this would
> > > overflow and no amount of dividing can recover the correct value.
>
> > ...
> >
> > > +	for (; max_chars > 0; max_chars--) {
> >
> > Less fragile is to write
> >
> > 	while (max_chars--)
>
> Except that the original was more obvious at least for me.
> I always prefer more readable code when the compiler might do
> the optimization easily. But this is my personal taste.
> I am fine with both variants.
>
> > This allows max_char to be an unsigned type.
> >
> > Moreover...
> >
> > > +	return _parse_integer_limit(s, base, p, INT_MAX);
> >
> > You have inconsistency with INT_MAX vs, size_t above.
>
> Ah, this was on my request. INT_MAX is already used on many other
> locations in vsnprintf() for this purpose.

Strictly speaking this should be SIZE_MAX because the argument is a
size_t.