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lib: fix _parse_integer_limit() to handle overflow

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Patch series "lib and lib/cmdline enhancements", v11.

This series is a merge of the recently posted [1] and [2].  The first one
is intended to adjust '_parse_integer_limit()' and 'memparse()' to not
ignore overflows, extend string to 64-bit integer conversion tests, add
KUnit-based test for 'memparse()' and fix kernel-doc glitches found in
lib/cmdline.c.  The second one was originated from RISCV-specific build
fixes needed to integrate the former and now aims to provide
platform-specific double-word shifts and corresponding KUnit test.

Getting feedback from RISCV core maintainers would be very helpful.

Special thanks to Andy Shevchenko, Charlie Jenkins, and Andrew Morton.


This patch (of 8):

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.

Link: https://lore.kernel.org/20260519172259.908980-1-dmantipov@yandex.ru
Link: https://lore.kernel.org/20260519172259.908980-2-dmantipov@yandex.ru
Link: https://lore.kernel.org/linux-riscv/20260403103338.1122415-1-dmantipov@yandex.ru [1]
Link: https://lore.kernel.org/linux-riscv/20260427090105.705529-1-dmantipov@yandex.ru [2]
Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andriy Shevchenko <andriy.shevchenko@intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Charlie Jenkins <thecharlesjenkins@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Dmitry Antipov 2026-05-19 20:22:52 +03:00 committed by Andrew Morton
parent dcc8a57815
commit 6e30111dbb
1 changed files with 22 additions and 15 deletions
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37
lib/kstrtox.c
View File

@ -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
*
* Return number of characters consumed maybe or-ed with overflow bit.
* If overflow occurs, result integer (incorrect) is still returned.
* Convert non-negative integer string representation in explicitly given
* radix to an integer. If overflow occurs, value at @p is set to ULLONG_MAX.
*
* Don't you dare use this function.
* This function is the workhorse of other string conversion functions and it
* is discouraged to use it explicitly. Consider kstrto*() family instead.
*
* 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