c50b6a2b89
Subtracting one from the smallest value expressable by the provided
variable could cause an underflow operation. In particular, this is
problematic when code similar to:
uint64_t foo = 0;
if (powerof2(foo)) {
...;
}
is run with integer sanitization enabled. The macro would subtract one
from zero, underflowing and triggering the sanitizer.
Make the powerof2() macro ubsan safe, by explicitly handling underflows.
Note: This change DOES NOT make powerof2() accurate. We continue to
falsely return "true" for 0 and negative numbers (see attached tests).
Found while investigating Bug: 122975762
Test: see added testcase
Test: atest ziparchive-tests
Change-Id: I5408ce5c18868d797bcae8f115ddb7c4c1ced81e
48 lines
1.5 KiB
C++
48 lines
1.5 KiB
C++
/*
|
|
* Copyright (C) 2019 The Android Open Source Project
|
|
*
|
|
* Licensed under the Apache License, Version 2.0 (the "License");
|
|
* you may not use this file except in compliance with the License.
|
|
* You may obtain a copy of the License at
|
|
*
|
|
* http://www.apache.org/licenses/LICENSE-2.0
|
|
*
|
|
* Unless required by applicable law or agreed to in writing, software
|
|
* distributed under the License is distributed on an "AS IS" BASIS,
|
|
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
|
|
* See the License for the specific language governing permissions and
|
|
* limitations under the License.
|
|
*/
|
|
|
|
#include <gtest/gtest.h>
|
|
#include <sys/param.h>
|
|
|
|
TEST(sys_param_test, powerof2_positives) {
|
|
ASSERT_TRUE(powerof2(1));
|
|
ASSERT_TRUE(powerof2(2));
|
|
ASSERT_TRUE(powerof2(4));
|
|
ASSERT_TRUE(powerof2(8));
|
|
ASSERT_FALSE(powerof2(3));
|
|
ASSERT_FALSE(powerof2(5));
|
|
ASSERT_FALSE(powerof2(7));
|
|
ASSERT_FALSE(powerof2(9));
|
|
ASSERT_FALSE(powerof2(10));
|
|
}
|
|
|
|
TEST(sys_param_test, powerof2_zero) {
|
|
// 0 isn't a power of 2, but for compatibility, we assume it is.
|
|
ASSERT_TRUE(powerof2(0));
|
|
uint32_t zero = 0;
|
|
ASSERT_TRUE(powerof2(zero));
|
|
}
|
|
|
|
TEST(sys_param_test, powerof2_negatives) {
|
|
// negative numbers can never be a power of 2, but for compatibility,
|
|
// we assume they can be.
|
|
int32_t min32 = INT32_MIN;
|
|
int64_t min64 = INT64_MIN;
|
|
ASSERT_TRUE(powerof2(min32));
|
|
ASSERT_FALSE(powerof2(min32 + 1));
|
|
ASSERT_TRUE(powerof2(min64));
|
|
ASSERT_FALSE(powerof2(min64 + 1));
|
|
}
|