Re: [PR] GH-36388: [C++][Array] Add Overflow check for string Repeat [arrow]

["js8544 (via GitHub)" <gi...@apache.org>]

js8544 commented on code in PR #38504:
URL: https://github.com/apache/arrow/pull/38504#discussion_r1385967985


##########
cpp/src/arrow/array/util.cc:
##########
@@ -669,11 +671,18 @@ class RepeatedArrayFactory {
   enable_if_base_binary<T, Status> Visit(const T&) {
     const std::shared_ptr<Buffer>& value = scalar<T>().value;
     std::shared_ptr<Buffer> values_buffer, offsets_buffer;
-    RETURN_NOT_OK(CreateBufferOf(value->data(), value->size(), &values_buffer));
     auto size = static_cast<typename T::offset_type>(value->size());
+
+    int64_t total_size;

Review Comment:
   Should this be `typename T::offset_type`? If `total_size` is fixed to be int64_t, it always calls the int64 version of `MultiplyWithOverflow`. But `StringArray` uses int32_t for offsets so some false positive cases can go through.
   For example:
   ```cpp
   auto scalar = std::make_shared<StringScalar>("aa");
   int64_t length = static_cast<int32_t>(std::numeric_limits<int32_t>::max()) / 2 + 1;
   auto array_result = MakeArrayFromScalar(*scalar, length);
   ```
   `array_result` will be `ok` but when I print the array it says `Invalid array: Negative offsets in binary array`



##########
cpp/src/arrow/array/array_test.cc:
##########
@@ -685,6 +685,19 @@ TEST_F(TestArray, TestMakeArrayFromScalarSliced) {
   }
 }
 
+TEST_F(TestArray, TestMakeArrayFromScalarOverflow) {
+  auto scalar = std::make_shared<StringScalar>("aa");
+
+  // Use a length that will cause an overflow when multiplied by the size of the string
+  int64_t length = static_cast<int64_t>(std::numeric_limits<int64_t>::max()) / 2 + 1;

Review Comment:
   We should probably test `StringArray` with `int32_t::max` and `LargeStringArray` with `int64_t::max`



##########
cpp/src/arrow/array/array_test.cc:
##########
@@ -685,6 +685,19 @@ TEST_F(TestArray, TestMakeArrayFromScalarSliced) {
   }
 }
 
+TEST_F(TestArray, TestMakeArrayFromScalarOverflow) {
+  auto scalar = std::make_shared<StringScalar>("aa");
+
+  // Use a length that will cause an overflow when multiplied by the size of the string
+  int64_t length = static_cast<int64_t>(std::numeric_limits<int64_t>::max()) / 2 + 1;
+  auto array_result = MakeArrayFromScalar(*scalar, length);
+
+  std::string err_msg = "offset overflow in repeated array construction";
+  ASSERT_FALSE(array_result.ok());
+  ASSERT_EQ(array_result.status().code(), StatusCode::Invalid);
+  ASSERT_EQ(array_result.status().message().substr(0, err_msg.length()), err_msg);

Review Comment:
   You can use `EXPECT_RAISES_WITH_MESSAGE_THAT(Invalid, ::testing::HasSubstr(err_msg), array_result);` to simplify this.



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