C++: Reuse bounded predicate in TaintedAllocationSize query #17220
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| category: minorAnalysis | ||
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| * The `cpp/uncontrolled-allocation-size` ("Uncontrolled allocation size") query now considers arithmetic operations that might reduce the size of user input as a barrier. The query therefore produces fewer false positive results. |
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@@ -180,6 +180,15 @@ void more_bounded_tests() { | |
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| int size = atoi(getenv("USER")); | ||
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| if (size % 100) | ||
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| malloc(size * sizeof(int)); // GOOD | ||
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There was a problem hiding this comment. Why is this example "GOOD", but the one from lines 132-136 isn't? There was a problem hiding this comment. I guess my actual question is: how is modulo supposed to bound the input here? There was a problem hiding this comment. That's a good point. It does not 😅. As it stands it's actually an example of a false negative. What I had in my mind was an example like this: int size = atoi(getenv("USER"));
int size2 = size % 100;
malloc(size2 * sizeof(int));There was a problem hiding this comment. Thanks for pointing this out @intrigus-lgtm. It's fixed now by #17269. |
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| int size = atoi(getenv("USER")); | ||
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Note that it's a pretty common pattern to have three cases to think about (1) a thing holds (2) the thing doesn't hold and (3) we weren't able to determine either. If we had another predicate,
convertedExprNeverOverflows, this would not be the inverse ofconvertedExprMightOverflow(due to case 3) and the choice between usingconvertedExprNeverOverflowsornot convertedExprMightOverflowas we do here would be meaningful.