Fix reading past end of array. #1468
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Fix a bug in the `NonDelegatingGetIids()` implementation that could cause reading past the end of the returned array. `std::copy()` returns a pointer to the next element in the array after the last element copied. The output argument `*array` was being assinged to this pointer after the first copy, causing it to no longer point to the beginning of the array. If the caller tries to access the full array after this, it will read past the end of the array and will miss the first elements of the array. To fix, introduce a new temporary `_array` variable to pass the result of the first copy as the starting point of the second copy. Also add a test that failed before the fix and passes after the fix.
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If we aren't going to merge #1467, this fixes a bug that was noted there. |
dmachaj
reviewed
Jan 14, 2025
| @@ -1033,8 +1033,8 @@ namespace winrt::impl | |||
| { | |||
| return error_bad_alloc; | |||
| } | |||
| *array = std::copy(local_iids.second, local_iids.second + local_count, *array); | |||
| std::copy(inner_iids.cbegin(), inner_iids.cend(), *array); | |||
| auto _array = std::copy(local_iids.second, local_iids.second + local_count, *array); | |||
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[nit] I think the name _array with the leading underscore is misaligned with the naming pattern in this code base. Something like array_copy or local_array would probably fit better.
| auto iids = winrt::get_interfaces(obj); | ||
| // BaseOverrides IID gets repeated twice. There are only 4 unique interfaces. | ||
| REQUIRE(iids.size() >= 4); |
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Maybe its just me, but >=4 seems overly conservative. If there is a well-known repeated IID then can this assert the size is 5 instead? Perhaps that's not ideal but it is at least testing the current behavior so that if it changes later the test will identify the behavior change.
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Fix a bug in the
NonDelegatingGetIids()implementation that could cause reading past the end of the returned array.std::copy()returns a pointer to the next element in the array after the last element copied. The output argument*arraywas being assinged to this pointer after the first copy, causing it to no longer point to the beginning of the array. If the caller tries to access the full array after this, it will read past the end of the array and will miss the first elements of the array.To fix, introduce a new temporary
_arrayvariable to pass the result of the first copy as the starting point of the second copy. Also add a test that failed before the fix and passes after the fix.