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C

C static code analysis

Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code

  • All rules 315
  • Vulnerability13
  • Bug76
  • Security Hotspot19
  • Code Smell207

  • Quick Fix 19
Filtered: 35 rules found
symbolic-execution
    Impact
      Clean code attribute
        1. The address of an automatic object should not be assigned to another object that may persist after the first object has ceased to exist

           Bug
        2. Variables should be initialized before use

           Bug
        3. Variables should not be accessed outside of their scope

           Bug
        4. Account validity should be verified when authenticating users with PAM

           Vulnerability
        5. Changing directories improperly when using "chroot" is security-sensitive

           Security Hotspot
        6. POSIX functions should not be called with arguments that trigger buffer overflows

           Vulnerability
        7. Server hostnames should be verified during SSL/TLS connections

           Vulnerability
        8. "pthread_mutex_t" should be unlocked in the reverse order they were locked

           Bug
        9. Only valid arguments should be passed to UNIX/POSIX functions

           Code Smell
        10. "pthread_mutex_t" should be properly initialized and destroyed

           Bug
        11. "pthread_mutex_t" should not be locked when already locked, or unlocked when already unlocked

           Bug
        12. Only valid arguments should be passed to stream functions

           Code Smell
        13. Using publicly writable directories is security-sensitive

           Security Hotspot
        14. Using clear-text protocols is security-sensitive

           Security Hotspot
        15. Blocking functions should not be called inside critical sections

           Code Smell
        16. Return value of "setuid" family of functions should always be checked

           Code Smell
        17. Size of variable length arrays should be greater than zero

           Code Smell
        18. "mktemp" family of functions templates should have at least six trailing "X"s

           Code Smell
        19. Appropriate size arguments should be passed to "strncat" and "strlcpy"

           Code Smell
        20. Server certificates should be verified during SSL/TLS connections

           Vulnerability
        21. Weak SSL/TLS protocols should not be used

           Vulnerability
        22. Integral operations should not overflow

           Bug
        23. Parameter values should be appropriate

           Bug
        24. Stack allocated memory and non-owned memory should not be freed

           Bug
        25. Closed resources should not be accessed

           Bug
        26. Dynamically allocated memory should be released

           Bug
        27. Freed memory should not be used

           Bug
        28. Memory locations should not be released more than once

           Bug
        29. Memory access should be explicitly bounded to prevent buffer overflows

           Bug
        30. Zero should not be a possible denominator

           Bug
        31. XML parsers should not be vulnerable to XXE attacks

           Vulnerability
        32. "nonnull" parameters and return values of "returns_nonnull" functions should not be null

           Bug
        33. Null pointers should not be dereferenced

           Bug
        34. Resources should be closed

           Bug
        35. Unused assignments should be removed

           Code Smell

        Freed memory should not be used

        intentionality - logical
        reliability
        Bug
        • cwe
        • symbolic-execution
        • cert

        Accessing a memory block that was already freed is undefined behavior. This rule flags access via a pointer or a reference to released heap memory.

        Why is this an issue?

        How can I fix it?

        More Info

        A program may allocate an additional memory block using the malloc function. When no longer needed, such memory blocks are released using the free function. After it is released, reading or writing to a heap-allocated memory block leads to undefined behavior.

        char *cp = (char*)malloc(sizeof(char)*10); // memory is allocated
        // all bytes in cp can be used here
        free(cp); // memory is released
        cp[9] = 0; // Noncompliant: memory is used after it was released
        

        In addition to the malloc and free pair, in C++ a heap memory may be acquired by use of the operator new, and later released using the operator delete.

        int *intArray = new int[20]; // memory is allocated
        // elements of intArray can be written or read here
        delete[] intArray; // memory is released
        intArray[3] = 10; // Noncompliant: memory is used after it was released
        

        Releasing a memory block by invoking free or operator delete informs the memory management system that the program no longer uses the given block. Depending on the state and load of the program, such block can be then:

        • reused, i.e., the allocation function returns the same pointer,
        • released to the operating system, making it inaccessible to the program.

        What is the potential impact?

        Accessing released memory causes undefined behavior. This means the compiler is not bound by the language standard anymore, and your program has no meaning assigned to it.

        Practically this has a wide range of effects:

        • The program may crash due to the memory no longer being accessible, or due to unexpected value being read or written via the pointer.
        • Reading from the released memory may produce a garbage value.
        • When the memory was already reused to store sensitive data, such as passwords, it may lead to a vulnerability that uses this defect to extract information from an instance of the program.
        • Writing to released memory may change the value of the unrelated object in a remote part of the code if the memory was reused by it. As different objects may reuse same the block of memory between runs, this leads to unintuitive and hard diagnose bugs.
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