See C17 7.1.4p1, which says, in part: Each of the following statements applies unless explicitly stated otherwise in the detailed descriptions that follow: 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 pointerto non-modifiable storage when the corresponding parameter is not const-qualified) or a type (after default argument promotion) not expected by a function with a variable number of arguments, the behavior is undefined. This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. SonarJava Version 5.9.2 (build 16552). Why do academics stay as adjuncts for years rather than move around? 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. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. ROSE does not handle cases where an allocation is assigned to an lvalue that is not a variable (such as a struct member or C++ function call returning a reference), Finds instances where a pointer is checked against NULL and then later dereferenced, Identifies functions that can return a null pointer but are not checked, Identifies code that dereferences a pointer and then checks the pointer against NULL, Can find the instances where NULL is explicitly dereferenced or a pointer is checked againstNULL but then dereferenced anyway. While the engine is in practice already able to explore code from other files if needed (relying solely on bytecode), we restrain this approach to a limited set of well-known methods from standard libraries, for which we know that behaviors are correctly produced. It could be non-null the first time but not the second time, sonar does not know this. The standard will simply copy 0 byteswhich is essentially a no-op. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Note that it doesn't know how to check for non-heap, non-stack. After that, you call res.getBody() again. - the incident has nothing to do with me; can I use this this way? Accessing or modifying a null object's field. I don't need to do this validation again. Is there a single-word adjective for "having exceptionally strong moral principles"? However, memory allocation > functions such as kstrdup() may fail and returns NULL. [4] To subscribe to this RSS feed, copy and paste this URL into your RSS reader. CWE-476: NULL Pointer Dereference: A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. NULL vs Uninitialized pointer - An uninitialized pointer stores an undefined value. I would also guess that pointers that point to the one-past-the-end of an array are also invalid. Aaron:I suspect we are talking past each other. In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. SONAR, SONARSOURCE, SONARLINT, SONARQUBE and SONARCLOUD are trademarks of SonarSource S.A. All other trademarks and copyrights are the property of their respective owners. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? Reports. Im having trouble understanding your problem. How can this new ban on drag possibly be considered constitutional? Unless explicitly stated otherwise in the description of a particular function in this subclause, pointer arguments on such a call shall still have valid values, as described in 7.1.4. sometimes FP occurs. context.RaiseException . It also reinforces the notion to the reader that any time you see arithmetic in an allocation expression, you need to think about corner-cases. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Revert Update S2259: "Null pointer dereference" CFG should ignore expressions in Debug.Assert #397 Introduce means to not raise "Expression always true/false" on values that were checked with Debug.Assert. When and how should I use a ThreadLocal variable? Thanks, David! To learn more, see our tips on writing great answers. IDE extension that lets you fix coding issues before they exist! The result of calling such a helper function should be . By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to bypass security measures. So we have to check all the arguments before performing any actions. Thus we should check > this kstrdup() operation. Optimizers are optimizing based on this latitude and have been for years. We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. At Connect and share knowledge within a single location that is structured and easy to search. In case the hash algorithm used for the signature is known to the OpenSSL library but the implementation of the hash algorithm is not available the digest initialization will fail. Shouldn't the function check all pointers before dereferencing them or passing them to another function? Using Kolmogorov complexity to measure difficulty of problems? What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? My question is; is my solution incorrect? Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? I'd guess null pointers are not valid, even though they point to 0 bytes. java Is null check needed before calling instanceof? rev2023.3.3.43278. Check whether a String is not Null and not Empty. the Java one). Then we hit memcpy with length 0. very old code or C code being worked into c++ may have functions that expect the user to delete the data. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. It does not point to any area of memory. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . isEmpty(Collection collection) Styling contours by colour and by line thickness in QGIS. Mutually exclusive execution using std::atomic? Is it possible to create a concave light? A reference to null should never be dereferenced/accessed. "After the incident", I started to be more careful not to trip over things. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. How to use java.net.URLConnection to fire and handle HTTP requests, Why should Java 8's Optional not be used in arguments, sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled. It's even called out explicitly in C17 7.24.1p2: Where an argument declared as size_t n specifies the length of the array for a function, n can have the value zero on a call to that function. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Some Interesting Facts: 1) void pointers cannot be dereferenced. best, such an exception will cause abrupt program termination. Asking for help, clarification, or responding to other answers. (from res.getBody().getServiceResult() ). The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar false-positive on rule: Null pointers should not be dereferenced, Null Pointer Dereference issue not detected when the pointer is returned by another function. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. }. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). Is there a single-word adjective for "having exceptionally strong moral principles"? And if there is no pointer_default declaration, then the default default is ref. But what exactly does it mean to "dereference a null pointer"? https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. Doing so will at best cause abrupt program termination, without the Unfortunately the problem is much more complex, and generally unsolvable within standard C. Consider the following example: There's no way f can check whether x points into valid memory or not. The approximation of the try catch flow is such that we consider an exception can be thrown just after the curly brace of the try. Just because something is a pointer does not mean you should call delete . PS: I also tried the code in android studio which uses Lint and got no warnings. In C, dereferencing a null pointer is undefined behavior. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. The null pointer check for writing or dereferencing should be a compiler flag or library setting. Correct; a null pointer is not a valid pointer for the C library functions. NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. positive S2637 in SonarQube 6.7.1 LTS, Sonar false positive, "change condition so that it does not always evaluate to true. The user_data pointer could be invalid in other ways, such as pointing to freed memory. Sonar is ok. Ticket opened : Thanks a lot for the minimalized reproducer ! At best, such an exception will cause abrupt program termination. I am a student implementing stack with singly linked list using C, following a book called Fundamentals of Data Structures in C.. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Powered by Discourse, best viewed with JavaScript enabled. (in the meantime, in case of any other false-positive suspicion, make sure to check those latest versions as bunch of improvements are regularly released). But passing 0 to memcpy() is not one of them. Why is there a voltage on my HDMI and coaxial cables? On the command prompt, the same arguments work and the record is added in db but not when I call the stored procedure from inside java program CallableStatement insertStat = db_conn.prepareCall (" {call InsertCourses (?,?,?,?,?,?,?,? http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. Two null pointers will always be equal to each other. Software Engineering Institute We cannot understand how there could be a null pointer exception at the reported line. Dereferencing a null pointer is undefined behavior. The above check can't hurt, as I guess you could have a system with a 32-bit size_t that had a ton of memory and had some crazy banking/selector scheme with pointers. My main problem is because I'm doing a restTemplate.exchange with try-catch and declaring a variable with null value before the clause try and then using it inside the try. However there is no portable way to verify that the pointer is valid, other than checking for null. Asking for help, clarification, or responding to other answers. False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. context.RaiseException , (/) And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). So Bar might not be initialized but then the last line of your example should not be evaluated in this case. At worst, it could expose debugging information that would be useful to an attacker, or sonarqube That is why I explicitly check for this in my attempted solution. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, It is a false positive, but it might be a good idea not to do the, Sonar false-positive on rule: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. Just a few words about the rule now. ), Does not guess that return values from malloc(), strchr(), etc., can be NULL (The return value from malloc() is NULL only if there is OOMo and the dev might not care to handle that. Why are physically impossible and logically impossible concepts considered separate in terms of probability? Using platform-specific means (e.g. You're in a company-managed project. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? This topic was automatically closed 7 days after the last reply. But even with this, the concerned object it tagged as a possible NullPointerException problem. HTTP request redirections should not be open to forging attacks Deserialization should not be vulnerable to injection attacks Endpoints should not be vulnerable to reflected cross-site scripting (XSS) attacks "CoSetProxyBlanket" and "CoInitializeSecurity" should not be used Database queries should not be vulnerable to injection attacks Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. sonarlint, sonarLint (3.2.) Making statements based on opinion; back them up with references or personal experience. Software project. Because a null pointer does not point to a meaningful object, an attempt to dereference(i.e., access the data stored at that memory location) a null pointer usually (but not always) causes a run-time error or immediate program crash. I could've fixed this by changing else to else if (B != null && B.length == 1), but doing so rewards me with warning "condition(B != null && B.length == 1) is always true". In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. Search for vulnerabilities resulting from the violation of this rule on the CERT website. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2, Sonar: Null pointers should not be dereferenced, Why should Java 8's Optional not be used in arguments, Sonar alert : "private" methods that don't access instance data should be "static", sonarLint complains "Null pointers should not be dereferenced (squid:S2259)" despite that possibility being handled, Java: (false?) Java Specification Participation Agreement version in use: 2.0. By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by .
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