In '_parse_integer_limit()', replace native integer arithmetic with 'check_mul_overflow()' and 'check_add_overflow()' to check whether an intermediate result goes out of range, and denote such a case with ULLONG_MAX. Adjust comment to kernel-doc style as well.
Signed-off-by: Dmitry Antipov <[email protected]> --- v2: initial version to join the series --- lib/kstrtox.c | 32 ++++++++++++++++++++------------ 1 file changed, 20 insertions(+), 12 deletions(-) diff --git a/lib/kstrtox.c b/lib/kstrtox.c index bdde40cd69d7..a416cdafee37 100644 --- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -39,20 +39,26 @@ const char *_parse_integer_fixup_radix(const char *s, unsigned int *base) return s; } -/* - * Convert non-negative integer string representation in explicitly given radix - * to an integer. A maximum of max_chars characters will be converted. +/** + * _parse_integer_limit - Convert integer string representation to an integer + * @s: Integer string representation + * @base: Radix + * @p: Where to store result + * @max_chars: Maximum amount of characters to convert + * + * Convert non-negative integer string representation in explicitly given + * radix to an integer. If overflow occurs, value at @p is set to ULLONG_MAX. * - * Return number of characters consumed maybe or-ed with overflow bit. - * If overflow occurs, result integer (incorrect) is still returned. + * This function is the workhorse of other string conversion functions and + * you do not expect to use it explicitly. Consider kstrto*() famlily instead. * - * Don't you dare use this function. + * Return: Number of characters consumed, maybe ORed with overflow bit */ noinline unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned long long *p, size_t max_chars) { - unsigned long long res; + unsigned long long tmp, res; unsigned int rv; res = 0; @@ -72,14 +78,16 @@ unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned lon if (val >= base) break; /* - * Check for overflow only if we are within range of - * it in the max base we support (16) + * Accumulate result if no overflow detected. + * Otherwise just consume valid characters. */ - if (unlikely(res & (~0ull << 60))) { - if (res > div_u64(ULLONG_MAX - val, base)) + if (res != ULLONG_MAX) { + if (check_mul_overflow(res, base, &tmp) || + check_add_overflow(tmp, val, &res)) { + res = ULLONG_MAX; rv |= KSTRTOX_OVERFLOW; + } } - res = res * base + val; rv++; s++; } -- 2.52.0
