null pointers should not be dereferenced

Thanks for contributing an answer to Stack Overflow! At Many platforms can support testing for those also. 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]. This is indeed an obvious False Positive from the rule. So you can declare a string t and then add characters to the string with a plus sign : t += 'a'; The code you are having issue with is just moving the pointer to the next character which the foreach is already doing. A non-null but invalid pointer passed to memcpy() can indeed cause undefined behavior, but that is not the issue in the noncompliant codethe pointer will either be valid or null. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . Then we hit memcpy with length 0. Note that 7.1.4 explicitly states that a null pointer is not a valid pointer argument. To learn more, see our tips on writing great answers. Just a few words about the rule now. Pointer is so confusing : Stack with singly linked list in C - Stack If you preorder a special airline meal (e.g. . The fact that you can't pass a null (no object) with a reference parameter can be a reason to use a pointer instead. When B is null, The control reaches inside the main if block only when length of A is 1. C# static code analysis: Null pointers should not be dereferenced Products In-IDE IDE extension that lets you fix coding issues before they exist! What is the point of Thrower's Bandolier? ", Eclipse - Sonar S2629 possible false positive with new String, SonarQube null pointers should not be dereferenced on try/catch, getTextContent() through "Null pointers should not be dereferenced". 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. Are there tables of wastage rates for different fruit and veg? If the project is not compiled, and without sonar.java.binaries whether the white list takes effect? ncdu: What's going on with this second size column? Null pointer - Wikipedia And the semantics, as I said, are different. I guess you could write a proposal to modify the C Standard, but our coding standard is meant to provide guidance for the existing language. What does it mean that a reference must refer to an object, not a dereferenced null pointer? extern char _etext; Because null pointer dereferencing is undefined behavior, the compiler (GCC in this case) can optimize away the if (!tun) check because it is performed after tun->sk is accessed, implying that tun is non-null. It's a modular system with the . It looks like a logic bug, which can cause a memory leaking. Replacing broken pins/legs on a DIP IC package, Bulk update symbol size units from mm to map units in rule-based symbology, How do you get out of a corner when plotting yourself into a corner. But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. My question is; is my solution incorrect? Find null smart pointer dereferences with the Clang Static Analyzer So the SIZE_MAX check was unnecessary. Why does Mister Mxyzptlk need to have a weakness in the comics? When length is zero, it is probably unusable condition for this function. > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to > the caller site. I feel my situation is not as complicated. SonarQube Version 6.7.2 (build 37468) The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. Ah, gotcha. res.getBody() == null || res.getBody().getServiceResult() == null). Styling contours by colour and by line thickness in QGIS. (from res.getBody().getServiceResult() ). The correct idiom is to only allocate storage if the pointer is currently NULL. When B is null, The control reaches inside the main if block only when length of A is 1. C# static code analysis: HTTP responses should not be vulnerable to Connect and share knowledge within a single location that is structured and easy to search. @Tibor SonarQube version 5.6.6, IntelliJ SonarLint plugin 3.0.0.2041, Sonar: Null pointers should not be dereferenced, How Intuit democratizes AI development across teams through reusability. The Clang Static Analyzer already has a checker to find the null pointer dereference in code, however it is not sufficient for higher abstractions such as C++ smart pointers or optionals. 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. When and how should I use a ThreadLocal variable? If not, this might be a bug. See the "Null pointer checks may be optimized away more aggressively" section inhttps://gcc.gnu.org/gcc-4.9/porting_to.htmlas an example with one common implementation. . With their flexibility, void pointers also bring some constraints. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. Clearly the standard enumerates 1 case of undefined behavior, but makes no special mention of n=0. How can we prove that the supernatural or paranormal doesn't exist? The method isNR(minRating) is a helper method that validate among other things, if the object minRating is null. The final NCCE is actually more insidious than it seems at first. CWE - CWE-476: NULL Pointer Dereference (4.10) - Mitre Corporation C static code analysis: Null pointers should not be dereferenced Is a PhD visitor considered as a visiting scholar? Thank you for clarifying your assertion until I understood it properly. 4500 Fifth Avenue Original Java Specification Request (JSR) - Java Community Process The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. in above code, Thanks for your relpy. There can be a null pointer type for each pointer type, such as a pointer to a character or a pointer to an integer, although this is . What Is the Difference Between 'Man' And 'Son of Man' in Num 23:19? I added an assertion to that compliant code example. This issues is displayed by SonarQube. Review and Fix Illegally Dereferenced Pointer Checks Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? vegan) just to try it, does this inconvenience the caterers and staff? (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). Issues Components. 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. I was fixing some issues gathered by SonarQube when I stumbled upon the following issue: "SonarQube violation: Possible null pointer dereference in ___ due to return value of called method" please explain null pointer dereference [Solved] (Java in General forum You can use Optional instead. Check whether a String is not Null and not Empty. http://blog.llvm.org/2011/05/what-every-c-programmer-should-know_14.html. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, SonarQube null pointers should not be dereferenced on try/catch, How Intuit democratizes AI development across teams through reusability. Sonar is ok. () What is null pointer exception in android. I'd guess WG14 has considered these questions, but I haven't until now :). By 'valid pointers' I mean that both src and dest pointers are not null and they both point to non-overlapping arrays containing at least n bytes each. 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. Asking for help, clarification, or responding to other answers. Making statements based on opinion; back them up with references or personal experience. And if there is no pointer_default declaration, then the default default is ref. the Java one). The expected result here is solve the issue with sonarqube. Likewise, pointers to freed memory are not valid. You need to benchmark. Explain about call by reference with an . So, this code should address the Sonar problem: You can also eliminate the null check using Optional>, like: Even I don't recommend this, you can just check the null responseDto without any use of Optional: Thanks for contributing an answer to Stack Overflow! Why is there a voltage on my HDMI and coaxial cables? It means this is illegal: T* p = nullptr; T& r = *p; // illegal NOTE: Please do not email us saying the above works on your particular version of your particular compiler. 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 (?,?,?,?,?,?,?,? How to fix int cannot be dereferenced? Explained by Sharing Culture The alert is related to the sonar rule : Null pointers should not be dereferenced. [PATCH v2] vsprintf: Do not have bprintf dereference pointers [SONARJAVA-2808] - Jira - SonarSource Best to cite C11 s7.24.2.1 here: The memcpy function copies n characters from the object pointed to by s2 into the object pointed to by s1. Consider the following scenario: you are asked to create a Java class MetaDisplay that contains a static void printTable(String r) method. How can we let this pass? SonarLint IntelliJ 4.0.0.2916 Java Rule 'Null pointers should not be dereferenced' I'm getting this fault in the next code when obj can't be null in any scenario. isEmpty(Map map) Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. it could allow an attacker to bypass security measures. [squid:S2259] False positive - "Null pointers should not be dereferenced" SonarQube - Null Pointer Dereference Issue java simonsirak (Simon Sirak) June 14, 2018, 1:18pm 1 Hi! Dereferencing a null pointer results in undefined behavior. Null pointer should not be dereferenced , And fwstr > is dereferenced in the following codes. The result of calling such a helper function should be . I've changed it to say null pointer instead of invalid pointer. Connect and share knowledge within a single location that is structured and easy to search. (I think you cover that in a different rule.) A reference to null should never be dereferenced/accessed. And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). Whats the grammar of "For those whose stories they are"? 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. Thanks for contributing an answer to Stack Overflow! Do "superinfinite" sets exist? To learn more, see our tips on writing great answers. 4. That's true. Is it possible to create a concave light? FindBugs CORRECTNESS - which would allow us to systematically observe what you are having. At best, such an exception will cause abrupt program termination. Trying to understand how to get this basic Fourier Series. The issue is: memcpy() and friends do not explicitly state that a null pointer is a valid pointer value, even if the number of bytes to copy is 0. [JAVA] 3.9 - FP for S2259 Null pointers should not be dereferenced Why pointers are not used in python? Explained by Sharing Culture (/). This compliant solution eliminates the null pointer deference by initializing sk to tun->sk following the null pointer check. What is a serialVersionUID and why should I use it? ), 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. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? The indicated severity is for this more severe case; on platforms where it is not possible to exploit a null pointer dereference to execute arbitrary code, the actual severity is low. Reports. Extended Description NULL pointer dereference issues can occur through a number of flaws, including race conditions, and simple programming omissions. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. How to deal with "java.lang.OutOfMemoryError: Java heap space" error? We can see that at obj.run(), obj can not be null, but is pointed out by Sonar. Share Improve this answer Follow answered Oct 5, 2017 at 16:27 util.regex.Matcher, java - Swing .getParent() . In Java, a special null value can be assigned to an object reference. What can a lawyer do if the client wants him to be acquitted of everything despite serious evidence? At worst, it could expose debugging information that would be useful to an attacker, or it could allow an attacker to . Trying to understand how to get this basic Fourier Series. Haiku is a free and open-source operating system for PC designed to be binary compatible with the BeOS operating system and embodying the basic ideas of BeOS. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. S2259: Null pointers should not be dereferenced java tsubasa (Jiaoyang Ma) January 11, 2019, 6:57am 1 versions used (SonarQube, Scanner, language analyzer) SonarQube Version 6.7.2 (build 37468) SonarJava Version 5.9.2 (build 16552) minimal code sample to reproduce (with analysis parameter, and potential instructions to compile). The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). Trying to understand how to get this basic Fourier Series. Null pointers should not be dereferenced. However there is no portable way to verify that the pointer is valid, other than checking for null. // <------- reported violation: NullPointerException might be thrown as 'bar' is nullable here, https://jira.sonarsource.com/browse/SONARJAVA-1490, https://groups.google.com/d/msgid/sonarqube/4752a999-246e-42c2-bbdc-8a44a5564ce9%40googlegroups.com. 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. In C# and Java, all reference types can point to null. The issue arises when dereferenced pointers are used. Doing so will cause a NullReferenceException to be thrown. Thanks for the feedback. A nonnegative return value represents the number of bytes successfully read (the return value is a "signed size" type, usually the native integer type for the target platform). The problem is that something like %*pbl which reads a bitmask, will save the pointer to the bitmask in the buffer. 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. ncdu: What's going on with this second size column? Alternate Terms Relationships SonarJava Version 5.9.2 (build 16552). . 1 Answer Sorted by: 2 Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. U1 merged - It is a great text book for learning about linux devices. There is no guarantee that subsequent invocations are returning the same value, thats why issue is raised. Can you please start a new thread and be more explicit about the issue you are observing. All content is copyright protected. Appropriate typecasting is necessary. sonarlint complains that Not the answer you're looking for? This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. Is null check needed before calling instanceof? We cannot understand how there could be a null pointer exception at the reported line. My code is GPL licensed, can I issue a license to have my code be distributed in a specific MIT licensed project? Why are Suriname, Belize, and Guinea-Bissau classified as "Small Island Developing States"? This compliant solution ensures that both input_str andthe pointer returned by malloc() are not null: This noncompliant code example is from a version of drivers/net/tun.c and affects Linux kernel 2.6.30 [Goodin 2009]: The sk pointer is initialized to tun->sk before checking if tun is a null pointer. Does a summoned creature play immediately after being summoned by a ready action? How can I check before my flight that the cloud separation requirements in VFR flight rules are met? , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Currently I'm working with SonarQube solving issues but I'm facing a trouble to how handle null pointers that shouldn't be dereferenced. versions used (SonarQube, Scanner, language analyzer) ii. That is why I explicitly check for this in my attempted solution. Removing the check "exception != null" raises S2259 "Null pointers should not be dereferenced" on "throw exception". Interactions/interfaces with C can't use references. NullPointerException is a RuntimeException. By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Dereferencing a null pointer is undefined behavior, typically abnormal program termination. Pointer Arithmetic in c - Unit - 4 1. Define pointer. Explain about the To learn more, see our tips on writing great answers. Sonar violation: Null pointers should not be dereferenced #7459 - GitHub If malloc() fails, it returns a null pointer that is assigned to c_str. Dereferencing a null pointer can lead to a denial of service. 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]. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. 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. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Is there a proper earth ground point in this switch box? The purpose of a NULL pointer is not to cause a processor exception when it is dereferenced (although that is nice to have for debugging.) I'd guess null pointers are not valid, even though they point to 0 bytes. sonar-java. A bug can cause them never to be reassigned. 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. PS: I also tried the code in android studio which uses Lint and got no warnings. SIZE_MAX is the largest possible value that a size_t could take, so it is not possible to have anything larger than SIZE_MAX. Because null pointer dereferencing is UB, the if (!tun) check can be elided entirely by the optimizer (since the tun->sk implies that tun must be non-null). Automated Detection Null pointer dereferences can happen in path-dependent ways. In layman's terms, a null pointer is a pointer to an address in the memory space that does not have a meaningful value and cannot be referenced by the calling program, for whatever reason. Software Engineering Institute 9.7 Null pointers - Learn C++ - LearnCpp.com context.RaiseException , (/) Find centralized, trusted content and collaborate around the technologies you use most. This solution also ensures that theuser_data pointer is not null. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. Fix S2583/S2589 FP: On null check if instance is used in try block - GitHub Hi Andreas, Thanks for the feedback. EXP01-J. Do not use a null in a case where an object is required specifies the length of the array for a function. raiseException() return, Sonar COMP-PROG-MODULE-5-6-REVIEWER.pdf - Pointers to string Made code more compliant with other rules. Even if the object is null in this case, it will not give an exception and will print ' null ' to the output stream. }. Calls to extension methods are not reported because they can still operate on null values. PS: I also tried the code in android studio which uses Lint and got no warnings. The nature of simulating nature: A Q&A with IBM Quantum researcher Dr. Jamie We've added a "Necessary cookies only" option to the cookie consent popup. sonarlint, sonarLint (3.2.) Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. PDF Fourth Coccinelle Workshop { Exercises 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". These can be: Invoking a method from a null object. New replies are no longer allowed. Not the answer you're looking for? [4] rev2023.3.3.43278. 2008-2023 SonarSource S.A., Switzerland. [RSPEC-2259] - Jira Is there a proper earth ground point in this switch box? A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. )}"); 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. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL.

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