In '_parse_integer_limit()', adjust native integer arithmetic with near-to-overflow branch where 'check_mul_overflow()' and 'check_add_overflow()' are used to check whether an intermediate result goes out of range, and denote such a case with ULLONG_MAX, thus making the function more similar to standard C library's 'strtoull()'. Adjust comment to kernel-doc style as well.
Reviewed-by: Andy Shevchenko <[email protected]> Signed-off-by: Dmitry Antipov <[email protected]> --- v8: do not use explicit temporary in check_xxx_overflow() calls and handle overflow flag using separate variable v7: drop redundant check against ULLONG_MAX and restore original comment v6: more compact for-loop and minor style adjustments again v5: minor brace style adjustment v4: restore plain integer arithmetic and use check_xxx_overflow() on near-to-overflow branch only v3: adjust commit message and comments as suggested by Andy v2: initial version to join the series --- lib/kstrtox.c | 37 ++++++++++++++++++++++--------------- 1 file changed, 22 insertions(+), 15 deletions(-) diff --git a/lib/kstrtox.c b/lib/kstrtox.c index bdde40cd69d7..cd67f494c3bd 100644 --- a/lib/kstrtox.c +++ b/lib/kstrtox.c @@ -39,25 +39,30 @@ 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 it + * is discouraged to use it explicitly. Consider kstrto*() family 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 int rv, overflow = 0; unsigned long long res; - unsigned int rv; res = 0; - rv = 0; - while (max_chars--) { + for (rv = 0; rv < max_chars; rv++, s++) { unsigned int c = *s; unsigned int lc = _tolower(c); unsigned int val; @@ -76,15 +81,17 @@ unsigned int _parse_integer_limit(const char *s, unsigned int base, unsigned lon * it in the max base we support (16) */ if (unlikely(res & (~0ull << 60))) { - if (res > div_u64(ULLONG_MAX - val, base)) - rv |= KSTRTOX_OVERFLOW; + if (check_mul_overflow(res, base, &res) || + check_add_overflow(res, val, &res)) { + res = ULLONG_MAX; + overflow = KSTRTOX_OVERFLOW; + } + } else { + res = res * base + val; } - res = res * base + val; - rv++; - s++; } *p = res; - return rv; + return rv | overflow; } noinline -- 2.53.0
