Fix undefined behavior in qsort comparison functions for rv_histogram #526
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The freq variable is of type size_t, but the qsort comparison functions were directly returning a->freq - b->freq, which implicitly converts the result to an int. This conversion can cause overflow, leading to implementation-defined behavior. When freq values are sufficiently large, this issue may violate the antisymmetric and transitive properties required for comparison functions: Antisymmetry: If a < b, then b > a. Transitivity: If a < b and b < c, then a < c. Violating these properties results in undefined behavior in qsort, which could trigger memory corruption in some glibc implementations, posing a potential security risk. [1] Rewrite the comparison functions (cmp_dec and cmp_asc) to compare size_t values explicitly, ensuring correctness and avoiding overflow. Link: https://www.qualys.com/2024/01/30/qsort.txt [1]
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Jan 24, 2025
Fix undefined behavior in qsort comparison functions for rv_histogram
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The freq variable is of type size_t, but the qsort comparison functions were directly returning a->freq - b->freq, which implicitly converts the result to an int. This conversion can cause overflow, leading to implementation-defined behavior.
When freq values are sufficiently large, this issue may violate the antisymmetric and transitive properties required for comparison functions:
Antisymmetry: If a < b, then b > a.
Transitivity: If a < b and b < c, then a < c.
Violating these properties results in undefined behavior in qsort, which could trigger memory corruption in some glibc implementations, posing a potential security risk. [1]
Rewrite the comparison functions (cmp_dec and cmp_asc) to compare size_t values explicitly, ensuring correctness and avoiding overflow.
Link: https://www.qualys.com/2024/01/30/qsort.txt [1]