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py/objint_mpz: Fix pow3 where third argument is zero.

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This finding is based on fuzzing MicroPython.  I manually minimized the
test case it provided.

Signed-off-by: Jeff Epler <jepler@gmail.com>
This commit is contained in:
Jeff Epler 2025-07-19 11:24:34 -05:00 committed by Damien George
parent ebc9525c95
commit 062e82a7cd
2 changed files with 9 additions and 3 deletions
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7
py/objint_mpz.c
View file

@ -356,9 +356,10 @@ static mpz_t *mp_mpz_for_int(mp_obj_t arg, mpz_t *temp) {
mp_obj_t mp_obj_int_pow3(mp_obj_t base, mp_obj_t exponent, mp_obj_t modulus) {
if (!mp_obj_is_int(base) || !mp_obj_is_int(exponent) || !mp_obj_is_int(modulus)) {
mp_raise_TypeError(MP_ERROR_TEXT("pow() with 3 arguments requires integers"));
} else if (modulus == MP_OBJ_NEW_SMALL_INT(0)) {
mp_raise_ValueError(MP_ERROR_TEXT("divide by zero"));
} else {
mp_obj_t result = mp_obj_new_int_from_ull(0); // Use the _from_ull version as this forces an mpz int
mp_obj_int_t *res_p = (mp_obj_int_t *)MP_OBJ_TO_PTR(result);
mp_obj_int_t *res_p = mp_obj_int_new_mpz();
mpz_t l_temp, r_temp, m_temp;
mpz_t *lhs = mp_mpz_for_int(base, &l_temp);
@ -376,7 +377,7 @@ mp_obj_t mp_obj_int_pow3(mp_obj_t base, mp_obj_t exponent, mp_obj_t modulus) {
if (mod == &m_temp) {
mpz_deinit(mod);
}
return result;
return MP_OBJ_FROM_PTR(res_p);
}
}
#endif

5
tests/basics/builtin_pow3_intbig.py
View file

@ -20,3 +20,8 @@ print(hex(pow(2, x-1, x))) # Should be 1, since x is prime
print(hex(pow(y, x-1, x))) # Should be 1, since x is prime
print(hex(pow(y, y-1, x))) # Should be a 'big value'
print(hex(pow(y, y-1, y))) # Should be a 'big value'
try:
print(pow(1, 2, 0))
except ValueError:
print("ValueError")