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.
I originally had UINT_MAX and changed on Petr's request to be consistent with other code. (Sorry Andy - my mistake not including you on the earlier review versions).
But 0 < INT_MAX < UINT_MAX, so ok to pass to an unsigned. And as Petr said on his original review, INT_MAX is "big enough".
I don't mind either way.
An alternative is to fix all the other locations. We would need to check if it is really safe. Well, I do not want to force Richard to fix this historical mess. He already put a lot lot of effort into fixing this long term issue.
...
- unsigned long long result;
- const char *cp;
- unsigned long long result = 0ULL; unsigned int rv;
- cp = _parse_integer_fixup_radix(cp, &base);
- rv = _parse_integer(cp, base, &result);
- if (max_chars == 0) {
cp = startp;goto out;- }
It's redundant if I'm not mistaken.
Also this is more obvious and less error prone from my POV. But I agree that it is redundant. I am not sure if this function is used in some fast paths.
Again I am fine with both variants.
- cp = _parse_integer_fixup_radix(startp, &base);
- if ((cp - startp) >= max_chars) {
cp = startp + max_chars;goto out;- }
This will be exactly the same, no?
Best Regards, Petr