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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

        "pthread_mutex_t" should not be locked when already locked, or unlocked when already unlocked

        intentionality - logical
        reliability
        Bug
        • cwe
        • symbolic-execution
        • multi-threading

        pthread_mutex_t should not be locked when already locked, or unlocked when already unlocked.

        Why is this an issue?

        How can I fix it?

        More Info

        Mutexes are synchronization primitives that allow to manage concurrency. This is the most fundamental building block for creating safe concurrent applications. By using a mutex, one can ensure that a block of code is executed by a single thread concurrently. Data structures are designed to maintain their invariants between member-function calls. If a data structure is accessed concurrently, and one of the accesses is a write operation, then it has a data race. Having data races is undefined behavior.

        Adversaries actively exploit data races to take over systems, but data races are also a common source of data corruption in concurrent applications resulting in dormant and hard-to-find bugs.

        To prevent data races, the shared resource (usually memory) must be protected by obtaining mutual access to the data during both reading and writing. Such mutual exclusion is generally achieved by using a mutex, which is frequently referred to as a lock.

        A mutex has two states: released - which is the initial state, or acquired. These two states are frequently called unlocked and locked as well.

        To effectively protect the shared resource from concurrent accesses, all such accesses should be guarded by the same mutex. They need to lock the mutex to gain safe exclusive access to the resource and unlock it after they are done mutating or reading it.

        You can abstract away the concurrent threads sharing the mutex and think of it as owned by the current thread. It never spontaneously changes between acquired and released.

        In this view, these are the possible transitions when calling lock or unlock on a mutex in a given state:

        1. released + lock() ⇒ acquired
        2. acquired + unlock() ⇒ released
        3. acquired + lock() ⇒ deadlock
        4. released + unlock() ⇒ undefined behavior

        When a thread locks a mutex, another thread trying to acquire the same mutex will be blocked and have to wait for the first thread to release it. This waiting period can take some time. If a thread attempts to lock a mutex it has already acquired, it will deadlock because it would need to release it to lock it again.

        What is the potential impact?

        Locking an acquired mutex leads to a deadlock, as a mutex can only be obtained once. Unlocking a released mutex is undefined behavior. Removing synchronization can cause data races, leading to data corruption, which adversaries might leverage to take over the system.

        Exceptions

        There are recursive mutexes that can be acquired multiple times by the same thread, given that just as many times we also release the mutex. They are rare in practice and usually signal design problems in the code. Thus we assume pthread_mutex_t refers to non-recursive mutexes.

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