C++: Add barriers to cpp/uncontrolled-allocation-size
#5903
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rdmarsh2
reviewed
May 14, 2021
| @@ -139,7 +139,7 @@ void more_bounded_tests() { | |||
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| if (size > 0) | |||
| { | |||
| malloc(size * sizeof(int)); // BAD | |||
| malloc(size * sizeof(int)); // GOOD (overflow not possible) | |||
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Could we add a test with a long to keep testing size > 0 with an actual overflow?
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Good point. I've done this in 31091c6. Sorry about the horrible diff from that commit. All it's doing is move a few lines and add the correct BAD result to the .expected file.
geoffw0
approved these changes
May 17, 2021
| // Subtracting two pointers is either well-defined (and the result will likely be small), or | ||
| // terribly undefined and dangerous. Here, we assume that the programmer has ensured that the | ||
| // result is well-defined (i.e., the two pointers point to the same object), and thus the result | ||
| // will likely be small. |
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Seems reasonable. If the subtraction result is not well-defined, that should probably be handled by another query (which may or may-not already exist) rather than blaming a later malloc.
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Indeed. 👍 I've opened up https://github.com/github/codeql-c-team/issues/525 for this exact query idea.
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(Part of https://github.com/github/codeql-c-team/issues/272.)
This PR adds two barriers to
cpp/uncontrolled-allocation-size:PointerDiffExpr. This is quite a common cause of false positives for this query. When I compare 5031b73 to 2d0a561) we get:This change doesn't seem to affect SAMATE.