So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. What should I follow, if two altimeters show different altitudes? There are other problems with this code, as is noted in the rule. I believe that dereferencing NULL should not crash the system, should not allow a write to a NULL pointer area, but should always set errno, If I am a hacker, could I trap a null failure that would force a memory dump. It would cause game actors to teleport to the wrong coordinates. very useful to find this very horrible bug in this case, we're using a pointer to memory which is not guaranteed to be zero, and potentially corrupting the malloc arena in the process. 0->member is undefined behavior. One could argue that all code examples would be redundant with the first pair. This table specifies different individual consequences associated with the weakness. If you want to change the value of your pointer, just do var1 = 0; Find centralized, trusted content and collaborate around the technologies you use most. Typical "easy to spot if you know there is a problem error". More specific than a Base weakness. Isn't easier just to check valid range of length? The code is dead and will be never processed because 'decoded' outside the scope and redefined in local. and Gary McGraw. /** I suppose there is a question of "Is a pointer that points to 0 bytes valid?" If all pointers that could have been modified are sanity-checked previous to use, nearly all NULL pointer dereferences can be prevented. <, [REF-1032] "Null Reference Creation and Null Pointer Dereference". int changed to size_t and if size_t parameter's is zero, allocate one word. In this case, the difference is the assumption thatmalloc() always returns non-nullfor the second NCCE, whereas the first NCCE has themalloc() abstracted away. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. I'm getting a warning while doing a Static Analysis (SA) on my code. 412-268-5800, If an argument to a function has an invalid value (such as a value outside the domain of the function, or a pointer outside the address space of the program, or a null pointer, or a pointer. If an invalid value has been assigned to the pointer, the behavior of the unary * operator is undefined.115). Note that it doesn't know how to check for non-heap, non-stack. Correct; a null pointer is not a valid pointer for the C library functions. FORWARD_NULL: A program will normally crash when a NULL pointer is dereferenced. Asking for help, clarification, or responding to other answers. @HemantBhargava - you may know that, but the code you have shown us does not ensure that. I added a comment to explain that SIZE_MAX is the limit of size_t. This was potentially problematic, due to the assert on an uninitialized variable. If it wasn't for coverity Resource leaks: I hate them, especially in libc, which is code you expect to be hot. Our code base contains a lot of copy paste mistakes, we are glad that there is a tool like coverity that can help to detect them. If you don't set it again before the above if statement, that means that the NULL check is unnecessary and should be removed. This weakness can be detected using dynamic tools and techniques that interact with the software using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. 565), Improving the copy in the close modal and post notices - 2023 edition, New blog post from our CEO Prashanth: Community is the future of AI. What is it that I did not understand? Example: tool developers, security researchers. I got the impression that 31 source files of Linux modules will need further adjustments. The two languages try to maximize compatibility, and occasionally succeed. It can never evaluate to true (unless Equals has been overridden to do something screwy). return p == NULL || (char *)p < &_etext; COVERITY checker description | The STAR experiment By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. which bolsters my assertion that x->member dereferences x (or at least an offset of x). That exception could have rendered the entire feature non operational (And many log messages that Unused value and previous write overwriting found in the defect meant error in algorithm. Coverity found a case where a copy/paste action went wrong. As a result, this noncompliant code example is vulnerable to a null pointer dereference exploit, because null pointer dereferencing can be permitted on several platforms, for example, by using mmap(2) with the MAP_FIXED flag on Linux and Mac OS X, or by using the shmat() POSIX function with the SHM_RND flag [Liu 2009]. Among the invalid values for dereferencing a pointer by the unary * operator are a null pointer, an address inappropriately aligned for the type of object pointed to, and the address of an object after the end of its lifetime. Would you become interested in a related clarification approach for a discussion topic like . Base - a weakness For example, there may be high likelihood that a weakness will be exploited to achieve a certain impact, but a low likelihood that it will be exploited to achieve a different impact. This noncompliant code example is derived from a real-world example taken from a vulnerable version of the libpng library as deployed on a popular ARM-based cell phone [Jack 2007]. Why does Acts not mention the deaths of Peter and Paul? These may be for specific named Languages, Operating Systems, Architectures, Paradigms, Technologies, or a class of such platforms. */. See "Clever Attack Exploits Fully-Patched Linux Kernel" [Goodin 2009] for an example of a code execution exploit that resulted from a null pointer dereference.
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