Avoid heap corruption with NULLs in TVPs (#1450) #1452
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The `GetParamType()` function calls `SQLDescribeParam()` and caches the type information it gets from the driver in a dynamically allocated array with one slot for each top-level parameter. This should not be done for nested table column "parameters" because: - that corrupts the heap when a TVP has more columns than slots; - it overwrites top-level parameter types with the wrong values; - `SQLDescribeParam()` fails for nested column "parameters" anyway. So for NULL TVP columns we fall back on SQL_VARCHAR. With the fix contained in this commit, the new test never fails (for my testing, at least). Without the fix, that test sometimes passes and sometimes crashes the Python interpreter (and *always* crashed Python when the `tests/__pycache__` directory was not present in my testing--not sure why 🤷♂️). Closes mkleehammer#1450
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@v-chojas I believe you created the original code to support TVPs, so if you have time to look at this PR, that would be much appreciated. |
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The
GetParamType()function callsSQLDescribeParam()and caches the type information it gets from the driver in a dynamically allocated array with one slot for each top-level parameter. This should not be done for nested table column "parameters" because:SQLDescribeParam()fails for nested column "parameters" anyway.So for NULL TVP columns we fall back on SQL_VARCHAR.
With the fix contained in this commit, the new test never fails (for my testing, at least). Without the fix, that test sometimes passes and sometimes crashes the Python interpreter (and always crashed Python when the
tests/__pycache__directory was not present in my testing--not sure why 🤷♂️).Closes #1450