null pointers should not be dereferenced null pointers should not be dereferenced

Null pointer should not be dereferenced . But passing 0 to memcpy() is not one of them. Made code more compliant with other rules. Is it possible to create a concave light? Find centralized, trusted content and collaborate around the technologies you use most. ncdu: What's going on with this second size column? 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. Believing that dereferencing NULL shouldn't crash the system doesn't make it true. This sounds indeed like a bug in the flow when an exception is raised. The same problem we will have with "Add at least one assertion to this test case." 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. (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). 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. 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. It is still a pointer though, to use it you just have to cast it to another kind of pointer first. Why do academics stay as adjuncts for years rather than move around? This engine is validating execution paths and checking for non-null values or null-check along the way, exploring all the possibilities. sonarlint complains that That is, sets equivalent to a proper subset via an all-structure-preserving bijection. 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 Two null pointers will always be equal to each other. That is why I explicitly check for this in my attempted solution. The libpng library allows applications to read, create, and manipulate PNG (Portable Network Graphics) raster image files. Can I tell police to wait and call a lawyer when served with a search warrant? 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. I don't need to do this validation again. , NPE : null-, . Hi @Michael! To learn more, see our tips on writing great answers. - the incident has nothing to do with me; can I use this this way? 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. On many platforms, dereferencing a null pointer results inabnormal program termination, but this is not required by the standard. For example the following program doesn't compile. The null pointer check for writing or dereferencing should be a compiler flag or library setting. We seem to have a false positive for "Null pointers should not be dereferenced" - squid:S2259. Correct; a null pointer is not a valid pointer for the C library functions. To learn more, see our tips on writing great answers. 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. which version of SonarQube are you using? In some situations, however, dereferencing a null pointer can lead to the execution of arbitrary code [Jack 2007,van Sprundel 2006]. . That is only true if possibleNumbers contains no element.. BTW: none of these warnings are shown by . And the semantics, as I said, are different. Powered by Discourse, best viewed with JavaScript enabled. Isn't easier just to check valid range of length? In this noncompliant code example, input_str is copied into dynamically allocated memory referenced by c_str. But when length of A is 1, the control never reaches the else block. Pittsburgh, PA 15213-2612 So Bar might not be initialized but then the last line of your example should not be evaluated in this case. Finally my method is returning a response with value of restTemplate. Java Specification Participation Agreement version in use: 2.0. sometimes FP occurs. Software Engineering Institute At this point we define size as strlen(input_str) + 1. The issue of passing n=0 to memcpy() is distinct from null or invalid pointers. io.NotSerializableException : java. A null pointer stores a defined value, but one that is defined by the environment to not be a valid address for any member or object. 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. Trying to understand how to get this basic Fourier Series. A reference to Nothing should never be dereferenced/accessed. (In contrast, the case of passing 0 bytes to malloc is addressed in C11.) Does a summoned creature play immediately after being summoned by a ready action? . Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. sonar-java. False-positives are pointed out in other SO posts (1 & 2), where nulls are involved across functions and procedures. This is indeed a false positive because, at time of writing, the sonarqube java analyzer (version 4.2.1 at time of writing) does not support cross procedural analysis and so it is not able to determine that indeed, for the condition to be true, the value of minRating has to be non null. Yeah, I suspect once it's possible to allocate 2+gigs contiguously in amainstream install of a modern OS, we'll see a frenzy of new vulnerabilities come out. I doubt that "length" of zero is a valid parameter, and although there no copy, but we see memory allocation. And fwstr > is dereferenced in the following codes. Much like dereferencing a dangling (or wild) pointer leads to undefined behavior, dereferencing a null pointer also leads to undefined behavior. The n=0 is a mildly interesting edge case: Clearly a pointer that points to at least one valid byte could be used as the src or dest pointer to a call to memcpy(, 0). In the simplest case, this function just returns the result of calling kmalloc. https://www.yammer.com/ http://feeds.feedburner.com/office/fmNx If you preorder a special airline meal (e.g. 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). Seems the analizer don't recognice the logic with the funcional object Optional. The idea is not to guarantee validity, but to catch a substantial number of problems that could occur. You can compare a pointer with NULL to test for the special condition. 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. 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?) The null concept refers to the idea that a pointer can hold a special value that is not equal to another pointer. Thanks for the feedback. Connect and share knowledge within a single location that is structured and easy to search. In C, dereferencing a null pointer is undefined behavior. I added a comment to explain that SIZE_MAX is the limit of size_t. A reference to null should never be dereferenced/accessed. Linear regulator thermal information missing in datasheet, Identify those arcade games from a 1983 Brazilian music video. Doing so will cause a NullReferenceException to be thrown. Aaron:I suspect we are talking past each other. Mutually exclusive execution using std::atomic? If copying takes place between objects that overlap, the behavior is undefined. String *x, y; X is a pointer to a string, Y is a string & = address of variable/ operator || referencing operator * = value of address || dereferencing operator Pointers = stores memory address as its variables NULL pointer = a constant with a value of zero defined || assigned to null Void pointer = a pointer that is not associated with any data types New operator = denotes a request for . You're in a company-managed project. That noncompliant code example (it's currently the 3rd) came from the Linux kernel, whose source is publicly available. 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). To create a custom null validation method declare an attribute with name ValidatedNotNullAttribute and mark the parameter that is Perhaps this could be done with a special constraint that will notify the SE engine that we learned from a Debug.Assert call. 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. If malloc() fails, it returns a null pointer that is assigned to c_str. Please direct comments on this JSR to the Spec Lead (s) Team. Setup is effortless and analysis is automatic for most languages, Fast, accurate analysis; enterprise scalability. At worst, it could expose debugging information that would be useful to an attacker or it could allow an Now, you can find the list of whitelisted methods here. The test was added to catch the possibly theoretical situation where the length of input_str was somehow the maximum size for size_t, and adding one to this size in the malloc expression (to allocated space for the trailing null byte) results in an integer overflow. Doing so will at best cause abrupt program termination, without the 1 Null pointers should not be dereferenced @CheckForNull String getName(){.} Recovering from a blunder I made while emailing a professor. 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. Report False-positive / False-negative [LTS] The new SonarQube LTS is here: SONARQUBE 9.9 LTS, SonarQube - Null Pointer Dereference Issue. This likely means that youre on an ancient version of the Java analyzer. 4500 Fifth Avenue 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". 0 is certainly within the 'domain of the function' (a phrase defined by mathematics but not by C11), as copying 0 bytes is well-understood (although silly). ", 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". I'd guess WG14 has considered these questions, but I haven't until now :). We can get a reference to point to null in the following ways: "uninitialized" reference type variables variables which are initialized with nulls and are assigned their real value afterward. Is it plausible for constructed languages to be used to affect thought and control or mold people towards desired outcomes? I believe in this case, either expression would work. When B is null, The control reaches inside the main if block only when length of A is 1. specifies the length of the array for a function. This is a matter of style, and also following code walkthrough. For the time being, I would unfortunately recommend to mark as False Positive the issue. 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 Not the answer you're looking for? Accessing or modifying a null object's field. I'd guess null pointers are not valid, even though they point to 0 bytes. Whoops, you're right. It's still illegal. 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. SonarLint: A "NullPointerException" could be thrown; "getBody()" can return null. Dereferencing a null pointer is undefined behavior. How to use Slater Type Orbitals as a basis functions in matrix method correctly? sonarqube Many platforms can support testing for those also. Asking for help, clarification, or responding to other answers. 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]. Discover SonarLint SaaS Setup is effortless and analysis is automatic for most languages Discover SonarCloud Self-Hosted Fast, accurate analysis; enterprise scalability Discover SonarQube Secrets ABAP 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. 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. In Java, a special null value can be assigned to an object reference. This topic was automatically closed 7 days after the last reply. positive S2637 in SonarQube 6.7.1 LTS, SonarQube for MSBuild not reporting quality issues, getTextContent() through "Null pointers should not be dereferenced". 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. To learn more, see our tips on writing great answers. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. When you have a variable of non-primitive type, it is a reference to an object. SonarJava Version 5.9.2 (build 16552). At ssize_t (*aio_read)(struct kiocb *, char __user *, size_t . By explicitly teaching the C++ standard class behaviors we can make the Analyzer to find more bugs related to modern C++ code. Should trycatch go inside or outside a loop? A bug can cause them never to be reassigned. 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. Is there a single-word adjective for "having exceptionally strong moral principles"? I feel my situation is not as complicated. 5.2 Part 2 Sometimes a helper function is de ned to perform the memory allocation. I would therefore assert that a platform whose memcpy() did anything besides a no-op when given n=0 and valid source/destination pointers was not C-standards-compliant. Description: This JSR will work to develop standard annotations (such as @NonNull) that can be applied to Java programs to assist tools that detect software defects. ability to run any cleanup processes. 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 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). 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. In C/C++ speak, 'dereferencing' simply means getting the object that a pointer . 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(). 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. If the pointer is not NULL, see if the assignment occurs only in a branch of a conditional statement.Investigate when that branch does not execute. (C11, S7.24.2.1). You need to benchmark. Appropriate typecasting is necessary. Is it possible to rotate a window 90 degrees if it has the same length and width? sonarlint, sonarLint (3.2.) By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. Making statements based on opinion; back them up with references or personal experience. uninitialized reference-type class members. Write a semantic patch to nd cases where the result of calling kmalloc is dereferenced with no previous NULL pointer test. SonarQube Version 6.7.2 (build 37468) Does it just mean failing to correctly check if a value is null? ii. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. 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.) If that variable hasn't had a reference assigned, it's a null reference, which (for internal/historical reasons) is referred to as a null pointer. Removing the check "exception != null" raises S2259 "Null pointers should not be dereferenced" on "throw exception". To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What are the effects of exceptions on performance in Java? Just a few words about the rule now. NullPointerException is a RuntimeException. rev2023.3.3.43278. In my experience, there are reasons to check for a NULL pointer other than dereferencing it. When length is zero, it is probably unusable condition for this function. Optimizers are optimizing based on this latitude and have been for years. I reordered that code example to do all the checks before allocations. It also uses the unsigned type size_t to pass the length parameter, ensuring that negative values are not passed to func(). Recovering from a blunder I made while emailing a professor. Sonar is ok. Sonar can't determine that the helper method did the null validation. C static code analysis: Null pointers should not be dereferenced C static code analysis Unique rules to find Bugs, Vulnerabilities, Security Hotspots, and Code Smells in your C code All rules 311 Vulnerability 13 Bug 74 Security Hotspot 18 Code Smell 206 Quick Fix 14 Tags "memset" should not be used to delete sensitive data Vulnerability By clicking Accept all cookies, you agree Stack Exchange can store cookies on your device and disclose information in accordance with our Cookie Policy. versions used (SonarQube, Scanner, language analyzer) Automated Detection Null pointer dereferences can happen in path-dependent ways. Likewise, pointers to freed memory are not valid. I've changed it to say null pointer instead of invalid pointer. 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]. raiseException() return, Sonar 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. When I added the not null validation as sonar suggest. When a variable is declared as being a pointer to type void, it is known as a generic pointer. (from res.getBody().getServiceResult() ). 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. I suppose we can check that that is not null, but we cannot check that it is valid (in any portable way). Rule squid:S2259 is based on a Symbolic Execution (SE) engine. This cross-file approach analysis can be quite resource-consuming, and we are not ready to openly enable the feature. The expected result here is solve the issue with sonarqube. Null pointers should not be dereferenced. Coverity Prevent cannot discover all violations of this rule, so further verification is necessary, Detects when NULL is dereferenced (Array of pointers is not checked. (I think you cover that in a different rule.) But the problem also exists in the compliant version, so I'm not so sure that it's really compliant. Thered be huge value in jumping onto the latest version of the ecosystem (notably SonarQube), and benefit from all latest analyzers (e.g. Essentially, this code and the previous dereference disagree as to whether this value is allowed to be null. And if there is no pointer_default declaration, then the default default is ref. "After the incident", I started to be more careful not to trip over things. Passing a null pointer tomemcpy() would produce undefined behavior, even if the number of bytes to copy were 0. We have a false positive with the " Null pointers should not be dereferenced -squid:S2259" rule : We have a "NullPointerException" false positive for which we do not know how to solve it. Your code needs to do something about the possible NullPointerException when some exception is caught, because in this scenario the responseDto will be null. 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. All content is copyright protected. 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. We can not disable any rule, sonar do validation in "Sonar way" (actual name of profile :) ), so we will need to mark them "Wont fix" each time it appear again in new code. Status: Dormant. sonarLint (3.2.) So Bar might not be initialized but then the last line of your example should not be evaluated in this case. SonarJava. My below code where I'm calling a stored procedure is giving a null pointer exception. Is the God of a monotheism necessarily omnipotent? Ticket opened : Thanks a lot for the minimalized reproducer ! () How can I check before my flight that the cloud separation requirements in VFR flight rules are met? In the first compliant example it's useless to do allocation if the essential pointer user_data is NULL. Here is our source code: Sign in to download full-size image We resolved it by adding our tools path in the white list, and repackaging it. What does "Could not find or load main class" mean? Which @NotNull Java annotation should I use? 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. Doing so will cause a NullPointerException to be thrown. Connect and share knowledge within a single location that is structured and easy to search. Staging Ground Beta 1 Recap, and Reviewers needed for Beta 2. If not, this might be a bug. This code also violates ERR33-C. Detect and handle standard library errors. 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. What does it mean that a reference must refer to an object, not a dereferenced null pointer? Reports. Finally, there is the matter of the compliant solution. There are other problems with this code, as is noted in the rule. Connect and share knowledge within a single location that is structured and easy to search. Then the reading of the buffer via bstr_printf() will then look at the pointer to process the final output. This is a feature that we are currently heavily working on to be able to switch off such kind of false positives. static-code-analysis Can you please start a new thread and be more explicit about the issue you are observing. Null pointer should not be dereferenced , In multithreaded programs, null pointer dereferences can violate cache coherency policies and can cause resource leaks.