null pointers should not be dereferenced

// <------- 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. What methods/tools can be used to determine the cause so that you stop the exception from causing the progra. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. It's a modular system with the . In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. Batch split images vertically in half, sequentially numbering the output files, Difficulties with estimation of epsilon-delta limit proof, Minimising the environmental effects of my dyson brain. Privacy Policy, Detect issues in your GitHub, Azure DevOps Services, Bitbucket Cloud, GitLab repositories. And if there is no pointer_default declaration, then the default default is ref. NullPointerException is a RuntimeException. When exploring such methods, the engine then deduces behaviors regarding null-checking (among other things). Shouldn't the function check all pointers before dereferencing them or passing them to another function? I don't need to do this validation again. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, S2259: Null pointers should not be dereferenced, find the list of whitelisted methods here, Rule java:S2259: False-positive NullPointerException bug logged when variable is null-checked by an imported method, What is the issue you are observing, in details, What version of SonarSource products you are using, as well as the version of SonarJava. Is there a single-word adjective for "having exceptionally strong moral principles"? 0 is a valid value as far as memcpy() is concerned, and malloc() has special language concerning malloc(0). By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. sonarlint, sonarLint (3.2.) Find centralized, trusted content and collaborate around the technologies you use most. We resolved it by adding our tools path in the white list, and repackaging it. How can we prove that the supernatural or paranormal doesn't exist? By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. SonarQube null pointers should not be dereferenced on try/catch, Sonarcube :Null pointers should not be dereferenced, How do you get out of a corner when plotting yourself into a corner. https://stackoverflow.com/questions/47534436/, https://stackoverflow.com/questions/47534436/, java - Jenkins groovy : Error: java. Issues Components. Issues Components. The standard will simply copy 0 byteswhich is essentially a no-op. Im currently using SonarQube version 5.6.6. better way to handle this is to store the result of method invocation in a variable. Instead use String.valueOf (object). validated for null in your method declaration with it: 2008-2023 SonarSource S.A., Switzerland. All rights are expressly reserved. Should trycatch go inside or outside a loop? The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. You can compare a pointer with NULL to test for the special condition. 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, This error was found in the following code: else if (foo.list().length > 0) { }, I attempted to resolve this by rewriting as: else if (null != foo.list() && foo.list().length > 0) { }, foo is an instance of the File class in Java, and is directly instantiated through new File(). What are the effects of exceptions on performance in Java? Null pointer should not be dereferenced . When c_str is dereferenced in memcpy(), the program exhibits undefined behavior. How do you ensure that a red herring doesn't violate Chekhov's gun? At best, such an exception will cause abrupt program termination. attacker to bypass security measures. That is why I explicitly check for this in my attempted solution. In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. Thanks for contributing an answer to Stack Overflow! Small typo nit: "such as if i t pointed to freed memory" meant to say "if it" instead (removing whitespace). How handle the initialization of "responseDto" without "null" because is throwing the issue on sonar. Null pointer should not be dereferenced , So no checking of the length is necessary (besides preventing integer overflow, which the compliant solution does). On such a call, a function that locates a character finds no occurrence, a function that compares two character sequences returns zero, and a function that copies characters copies zero characters. When and how should I use a ThreadLocal variable? Its purpose is to serve as a special value for a pointer that could indicate a special condition in your program. Description The program can potentially dereference a null pointer, thereby raising a NullPointerException. very old code or C code being worked into c++ may have functions that expect the user to delete the data. public boolean isNameEmpty() { return getName().length() == 0; // Noncompliant; the result of getName() could be null, but isn't null-checked } . 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]. extern char _etext; So let me be more precise in my wording: I assert that a platform whose memcpy() did anything besides copy zero bytes when given n=0 and valid src and dest pointers was not C-standards-compliant. LANG.MEM.NPDLANG.STRUCT.NTADLANG.STRUCT.UPD, Null pointer dereferenceNull test after dereferenceUnchecked parameter dereference, Can detect violations of this rule. After that, you call res.getBody() again. res.getBody() == null || res.getBody().getServiceResult() == null). False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. 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. Just because something is a pointer does not mean you should call delete . Making statements based on opinion; back them up with references or personal experience. Thanks for contributing an answer to Stack Overflow! To be precise, once length is changed to a size_t and cannot take negative values, it cannot have an invalid value. 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. void *pointerVariableName = NULL; Since they are very general in nature, they are also known as generic pointers. Reports. Connect and share knowledge within a single location that is structured and easy to search. 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. Explain about call by reference with an . Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. We might set a pointer to null even if we are not freeing a object, simply to dissociate one object from another: tty_driver->tty = NULL; /* detach low level driver from the tty device */ Null pointers should not be dereferenced. 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. Thanks for the feedback. return p == NULL || (char *)p < &_etext; Accessing or modifying a null object's field. Why are physically impossible and logically impossible concepts considered separate in terms of probability? What is generic pointer? I already tried to put ResponseEntity responseDto inside my try clause assigning and returning the respective value but its mandatory to return something out the try/catch. We really appreciate your help. 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. I believe in this case, either expression would work. But when length of A is 1, the control never reaches the else block. In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks. These can be: Invoking a method from a null object. There are other problems with this code, as is noted in the rule. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Doing so will cause a NullReferenceException to be thrown. Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide, how to handle Sonarlint java:S2259 (Null pointers should not be dereferenced), How Intuit democratizes AI development across teams through reusability. 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. Your assertion is not backed by the wording in the standard, nor by common implementer understanding. Java Specification Participation Agreement version in use: 2.0. Which ensures that the chunkdata pointer is valid, but makes no such check to the user_data pointer. Im very new to sonar, is there a way to add methods to the whitelist? A common memory-leak idiom, is reallocating storage and assigning its address to a pointer that already points to allocated storage. - the incident has nothing to do with me; can I use this this way? Rule squid:S2259 is based on a Symbolic Execution (SE) engine. Did any DOS compatibility layers exist for any UNIX-like systems before DOS started to become outmoded? https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx Im having trouble understanding your problem. Styling contours by colour and by line thickness in QGIS. The 2nd NCCE/CS pair seems redundant with the first NCCE/CS pair. vegan) just to try it, does this inconvenience the caterers and staff? Is it possible to create a concave light? Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. I think "res.getBody() == null" checks null first so it should go to return line, not reach to next if condition. At this point we define size as strlen(input_str) + 1. ability to run any cleanup processes. 3.Null pointers should not be derefer enced/accessed. And fwstr > is dereferenced in the following codes. So we have to check all the arguments before performing any actions. 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. It does not point to any area of memory. 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.) 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. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? Browse other questions tagged, Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide. Is there a single-word adjective for "having exceptionally strong moral principles"? 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. Thus we should check > this kstrdup() operation. Making statements based on opinion; back them up with references or personal experience. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. Does Java have support for multiline strings? sonar-java. Unlike reference types, pointer types are not tracked by the default garbage . Is there a solution to add special characters from software and how to do it, Acidity of alcohols and basicity of amines. If you say [in] or [out] without a modifier, then the modifier defaults to the pointer_default for the enclosing class. 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]. 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. Maybe one of these methods is already doing what your methods is doing, and could be considered as replacement. Do not use a null in a case where an object is required, https://gcc.gnu.org/gcc-4.9/porting_to.html, Prior to 2018-01-12: CERT: Unspecified Relationship, Pointer Casting and Pointer Type Changes [HFC], Dereferencing an out-of-domain pointer [nullref], Section 5.2.18, "Null-Pointer Dereference", Dereferencing null pointers that were not returned by a function. What is null pointer exception in android. Not the answer you're looking for? points to memory allocated to the process) and what exactly was allocated there after the public key was freed, this may cause a segmentation fault or even execute code, which could again cause a segmentation fault, but might potentially be under the attacker's control. "After the incident", I started to be more careful not to trip over things. The value 0 for the number of bytes to copy is not what causes the UB, it's the null pointer value which triggers it. Obviously the value of that pointer could have changed since the . The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Ah, gotcha. How to tell which packages are held back due to phased updates. That is, sets equivalent to a proper subset via an all-structure-preserving bijection. This code also violates ERR33-C. Detect and handle standard library errors. But passing 0 to memcpy() is not one of them. How can I check before my flight that the cloud separation requirements in VFR flight rules are met? And the compliant solution guarantees that the pointer will be valid if the code calls memcpy(). Automated Detection Null pointer dereferences can happen in path-dependent ways. The problem is that something like %*pbl which reads a bitmask, will save the pointer to the bitmask in the buffer. ncdu: What's going on with this second size column? Optimizers are optimizing based on this latitude and have been for years. The return value from strchr() is often NULL, but the dev might know that a specific strchr() function call will not return NULL. Trying to understand how to get this basic Fourier Series. Thanks for your relpy. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. 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. , RemoteContext new ExceptionType() RemoteContext , SonarLintJava (), java - sonarLint "Null pointers should not be dereferenced (squid:S2259)"Stack Overflow Dereferencing a null pointer is undefined behavior, typically abnormal program termination. I'd guess WG14 has considered these questions, but I haven't until now :). 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. When length is zero, it is probably unusable condition for this function. 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. At best, such an exception will cause abrupt program termination. Can I tell police to wait and call a lawyer when served with a search warrant? Key here (explains table format and definitions), EXP34-C = Union( CWE-690, list) where list =. My question is; is my solution incorrect? To subscribe to this RSS feed, copy and paste this URL into your RSS reader. This likely means that youre on an ancient version of the Java analyzer. Please direct comments on this JSR to the Spec Lead (s) Team. A reference to null should never be dereferenced/accessed. The final NCCE is actually more insidious than it seems at first. Using Kolmogorov complexity to measure difficulty of problems? sometimes FP occurs. PS: I also tried the code in android studio which uses Lint and got no warnings. What does "Could not find or load main class" mean? For example the following program doesn't compile. > Further, if kstrdup() returns NULL, we should return ERR_PTR(-ENOMEM) to > the caller site. Why do academics stay as adjuncts for years rather than move around? (I think you cover that in a different rule.) The same problem we will have with "Add at least one assertion to this test case." You need to benchmark. How do I align things in the following tabular environment? The alert is related to the sonar rule : Null pointers should not be dereferenced. But even with this, the concerned object it tagged as a possible NullPointerException problem. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. How to use Slater Type Orbitals as a basis functions in matrix method correctly? To learn more, see our tips on writing great answers. 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. Does a summoned creature play immediately after being summoned by a ready action? When I scan with sonar-lint in idea, it seams white list is useful, but when use sonar-scanner, always FP, org.springframework.util.CollectionUtils#isEmpty 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). This solution also ensures that theuser_data pointer is not null. It is generally accepted that zeroing a pointer is a good way to mark it as invalid and dereferencing an invalid pointer is a bug. Ticket opened : Thanks a lot for the minimalized reproducer ! Is the God of a monotheism necessarily omnipotent? Why is there a voltage on my HDMI and coaxial cables? parsing /proc/self/maps under linux) one might find out whether the pointer points into mapped memory, but this is still not a guarantee of validity because it is very coarse-grained see again the above example. If you write [ref], then a null pointer is not allowed, but if you write [unique], then a null pointer is permitted. () You're in a company-managed project. I feel my situation is not as complicated. If the project is not compiled, and without sonar.java.binaries whether the white list takes effect? NULL vs Void Pointer - Null pointer is a value, while void pointer is a type. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. Using platform-specific means (e.g. To learn more, see our tips on writing great answers. Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. best, such an exception will cause abrupt program termination. NULL vs Uninitialized pointer - An uninitialized pointer stores an undefined value. I have a sonar alert on this call minRating.getRatgCaam(). Appropriate typecasting is necessary. How can we prove that the supernatural or paranormal doesn't exist? specifies the length of the array for a function. Check whether a String is not Null and not Empty. The problem is, I hope this code's result to be <5,3> and <9,6> BUT the console only shows me <5,3> and <9,3>. The article easily misleads the reader into believeing that ensuring pointer validity boils down to checking for pointer being not equal to NULL. ucsi->connector gets dereferenced by both ucsi_connector_change() and ucsi_resume(), both check for ucsi->connector being NULL in case ucsi_init() has not finished yet; or in case ucsi_init() has failed. When B is null, The control reaches inside the main if block only when length of A is 1. That interpretation of the standard is not supported universally. 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. Possible fix: Assign a valid address to the pointer in all branches of the conditional statement.. Pointer can point to dynamically allocated memory. Dereferencing a null pointer can lead to a denial of service. sonarlint complains that which would allow us to systematically observe what you are having. 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. raiseException() return, Sonar (from res.getBody().getServiceResult() ). One could argue that all code examples would be redundant with the first pair. Find centralized, trusted content and collaborate around the technologies you use most. 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. null(java.lang.NullPointerException) . SonarJava. Not the answer you're looking for? Additionally, if input_str is a null pointer, the call to strlen() dereferences a null pointer, also resulting in undefined behavior. That makes sense. This compliant solution ensures that the pointer returned by png_malloc() is not null. EXP34-C is a common consequence of ignoring function return values, but it is a distinct error, and can occur in other scenarios too. Dereferencing a null pointer is undefined behavior. To learn more, see our tips on writing great answers. I added a comment to explain that SIZE_MAX is the limit of size_t. In the meantime, Im locking this thread. the Java one). All content is copyright protected. Could I capture, and I would be able to glean much security information from the dump? 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. Is there a proper earth ground point in this switch box? PS: I also tried the code in android studio which uses Lint and got no warnings. When B is null, The control reaches inside the main if block only when length of A is 1. Unfortunately, its actual state also has some limitations, like the one you are hitting here. What is a serialVersionUID and why should I use it? Since you cannot have a variable of type void, the pointer will not point to any data and therefore cannot be dereferenced. 3.7. IDE extension that lets you fix coding issues before they exist! By clicking Post Your Answer, you agree to our terms of service, privacy policy and cookie policy. Fixed by #1156 Contributor 94cb5f8 boris-unckel on Jul 28, 2021 9e62550 boris-unckel mentioned this issue on Jul 28, 2021 Closes #1155 - Null pointers should not be dereferenced #1156 Merged 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. Correct; a null pointer is not a valid pointer for the C library functions. ncdu: What's going on with this second size column? A value is checked here to see whether it is null, but this value can't be null because it was previously dereferenced and if it were null a null pointer exception would have occurred at the earlier dereference. Making statements based on opinion; back them up with references or personal experience. New replies are no longer allowed. You do not have permission to delete messages in this group, Either email addresses are anonymous for this group or you need the view member email addresses permission to view the original message. Connect and share knowledge within a single location that is structured and easy to search. I suppose there is a question of "Is a pointer that points to 0 bytes valid?" In the simplest case, this function just returns the result of calling kmalloc. If malloc() fails, it returns a null pointer that is assigned to c_str. The solution that I recommend is not work with null returns or variables on Java, try to avoid it. 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" It looks like a logic bug, which can cause a memory leaking. It is useful to have a function with portable interface but platform-dependent implementation: extern bool invalid(const void *); Asking for help, clarification, or responding to other answers. By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. Likewise, pointers to freed memory are not valid. I've changed it to say null pointer instead of invalid pointer. Doing so will at best cause abrupt program termination, without the 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?)

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